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 $194.78   4.852%   $204.2307   $204.23   $204.25   $204.20  
  Purchase #2 $144.58   11.679%   $161.4655   $161.47   $161.45   $161.50  
  Purchase #3 $87.43   7.525%   $94.0091   $94.01   $94.00   $94.00  
  Purchase #4 $130.86   3.464%   $135.393   $135.39   $135.40   $135.40  
  Purchase #5 $205.82   5.603%   $217.3521   $217.35   $217.35   $217.40  
  Purchase #6 $75.69   13.646%   $86.0187   $86.02   $86.00   $86.00  
  Purchase #7 $43.26   6.149%   $45.9201   $45.92   $45.90   $45.90  
  7 purchase totals = $882.42       $944.3892   $944.39   $944.35   $944.40