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 $232.43   5.386%   $244.9487   $244.95   $244.95   $244.90  
  Purchase #2 $97.80   8.533%   $106.1453   $106.15   $106.15   $106.10  
  Purchase #3 $98.38   10.275%   $108.4885   $108.49   $108.50   $108.50  
  Purchase #4 $92.79   11.322%   $103.2957   $103.30   $103.30   $103.30  
  Purchase #5 $102.33   8.414%   $110.94   $110.94   $110.95   $110.90  
  Purchase #6 $211.95   8.853%   $230.7139   $230.71   $230.70   $230.70  
  Purchase #7 $42.77   13.348%   $48.4789   $48.48   $48.50   $48.50  
  7 purchase totals = $878.45       $953.0110   $953.02   $953.05   $952.90