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 $87.66   8.491%   $95.1032   $95.10   $95.10   $95.10  
  Purchase #2 $194.79   13.827%   $221.7236   $221.72   $221.70   $221.70  
  Purchase #3 $113.91   10.599%   $125.9833   $125.98   $126.00   $126.00  
  Purchase #4 $25.87   8.304%   $28.0182   $28.02   $28.00   $28.00  
  Purchase #5 $184.71   12.442%   $207.6916   $207.69   $207.70   $207.70  
  Purchase #6 $63.57   10.450%   $70.2131   $70.21   $70.20   $70.20  
  Purchase #7 $12.29   13.853%   $13.9925   $13.99   $14.00   $14.00  
  7 purchase totals = $682.80       $762.7255   $762.71   $762.70   $762.70