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 $86.61   9.796%   $95.0943   $95.09   $95.10   $95.10  
  Purchase #2 $182.35   6.770%   $194.6951   $194.70   $194.70   $194.70  
  Purchase #3 $67.42   13.751%   $76.6909   $76.69   $76.70   $76.70  
  Purchase #4 $9.44   12.335%   $10.6044   $10.60   $10.60   $10.60  
  Purchase #5 $118.87   5.394%   $125.2818   $125.28   $125.30   $125.30  
  Purchase #6 $208.28   11.802%   $232.8612   $232.86   $232.85   $232.90  
  Purchase #7 $222.54   9.627%   $243.9639   $243.96   $243.95   $244.00  
  7 purchase totals = $895.51       $979.1916   $979.18   $979.20   $979.30