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 $87.53   9.163%   $95.5504   $95.55   $95.55   $95.60  
  Purchase #2 $97.42   5.279%   $102.5628   $102.56   $102.55   $102.60  
  Purchase #3 $98.40   13.656%   $111.8375   $111.84   $111.85   $111.80  
  Purchase #4 $118.55   11.837%   $132.5828   $132.58   $132.60   $132.60  
  Purchase #5 $107.43   3.251%   $110.9225   $110.92   $110.90   $110.90  
  Purchase #6 $151.95   3.761%   $157.6648   $157.66   $157.65   $157.70  
  Purchase #7 $151.67   8.157%   $164.0417   $164.04   $164.05   $164.00  
  7 purchase totals = $812.95       $875.1625   $875.15   $875.15   $875.20