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 $88.46   4.637%   $92.5619   $92.56   $92.55   $92.60  
  Purchase #2 $102.71   6.799%   $109.6933   $109.69   $109.70   $109.70  
  Purchase #3 $111.84   4.212%   $116.5507   $116.55   $116.55   $116.60  
  Purchase #4 $212.38   9.254%   $232.0336   $232.03   $232.05   $232.00  
  Purchase #5 $208.90   6.221%   $221.8957   $221.90   $221.90   $221.90  
  Purchase #6 $119.75   12.753%   $135.0217   $135.02   $135.00   $135.00  
  Purchase #7 $82.89   6.379%   $88.1776   $88.18   $88.20   $88.20  
  7 purchase totals = $926.93       $995.9345   $995.93   $995.95   $996.00