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 $113.62   10.611%   $125.6762   $125.68   $125.70   $125.70  
  Purchase #2 $97.40   9.138%   $106.3004   $106.30   $106.30   $106.30  
  Purchase #3 $175.51   10.637%   $194.179   $194.18   $194.20   $194.20  
  Purchase #4 $83.70   10.848%   $92.7798   $92.78   $92.80   $92.80  
  Purchase #5 $75.54   4.132%   $78.6613   $78.66   $78.65   $78.70  
  Purchase #6 $224.94   3.328%   $232.426   $232.43   $232.45   $232.40  
  Purchase #7 $98.84   10.203%   $108.9246   $108.92   $108.90   $108.90  
  7 purchase totals = $869.55       $938.9473   $938.95   $939.00   $939.00