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 $197.37   5.872%   $208.9596   $208.96   $208.95   $209.00  
  Purchase #2 $96.65   6.211%   $102.6529   $102.65   $102.65   $102.70  
  Purchase #3 $85.70   6.300%   $91.0991   $91.10   $91.10   $91.10  
  Purchase #4 $10.50   8.289%   $11.3703   $11.37   $11.35   $11.40  
  Purchase #5 $215.53   13.435%   $244.4865   $244.49   $244.50   $244.50  
  Purchase #6 $40.38   5.476%   $42.5912   $42.59   $42.60   $42.60  
  Purchase #7 $51.80   12.314%   $58.1787   $58.18   $58.20   $58.20  
  7 purchase totals = $697.93       $759.3383   $759.34   $759.35   $759.50