Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $161.54   9.536%   $176.9445   $176.94   $176.95   $176.90  
  Purchase #2 $150.53   8.352%   $163.1023   $163.10   $163.10   $163.10  
  Purchase #3 $203.34   11.196%   $226.1059   $226.11   $226.10   $226.10  
  Purchase #4 $178.58   3.657%   $185.1107   $185.11   $185.10   $185.10  
  Purchase #5 $204.67   4.136%   $213.1352   $213.14   $213.15   $213.10  
  Purchase #6 $114.43   11.200%   $127.2462   $127.25   $127.25   $127.20  
  Purchase #7 $245.98   9.560%   $269.4957   $269.50   $269.50   $269.50  
  7 purchase totals = $1,259.07       $1,361.1405   $1,361.15   $1,361.15   $1,361.00