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 $167.50   8.216%   $181.2618   $181.26   $181.25   $181.30  
  Purchase #2 $213.86   9.295%   $233.7383   $233.74   $233.75   $233.70  
  Purchase #3 $232.57   13.421%   $263.7832   $263.78   $263.80   $263.80  
  Purchase #4 $196.55   4.281%   $204.9643   $204.96   $204.95   $205.00  
  Purchase #5 $214.33   13.683%   $243.6568   $243.66   $243.65   $243.70  
  Purchase #6 $132.34   3.721%   $137.2644   $137.26   $137.25   $137.30  
  Purchase #7 $182.30   9.800%   $200.1654   $200.17   $200.15   $200.20  
  7 purchase totals = $1,339.45       $1,464.8342   $1,464.83   $1,464.80   $1,465.00