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 $193.74   11.359%   $215.7469   $215.75   $215.75   $215.70  
  Purchase #2 $59.34   4.675%   $62.1141   $62.11   $62.10   $62.10  
  Purchase #3 $66.38   5.528%   $70.0495   $70.05   $70.05   $70.00  
  Purchase #4 $220.92   5.693%   $233.497   $233.50   $233.50   $233.50  
  Purchase #5 $128.45   5.377%   $135.3568   $135.36   $135.35   $135.40  
  Purchase #6 $45.25   5.859%   $47.9012   $47.90   $47.90   $47.90  
  Purchase #7 $19.53   6.523%   $20.8039   $20.80   $20.80   $20.80  
  7 purchase totals = $733.61       $785.4694   $785.47   $785.45   $785.40