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 $234.56   12.113%   $262.9723   $262.97   $262.95   $263.00  
  Purchase #2 $211.50   7.209%   $226.747   $226.75   $226.75   $226.70  
  Purchase #3 $105.29   4.690%   $110.2281   $110.23   $110.25   $110.20  
  Purchase #4 $53.58   4.780%   $56.1411   $56.14   $56.15   $56.10  
  Purchase #5 $197.71   8.208%   $213.938   $213.94   $213.95   $213.90  
  Purchase #6 $119.43   6.761%   $127.5047   $127.50   $127.50   $127.50  
  Purchase #7 $187.70   3.718%   $194.6787   $194.68   $194.70   $194.70  
  7 purchase totals = $1,109.77       $1,192.2099   $1,192.21   $1,192.25   $1,192.10