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 $208.38   8.808%   $226.7341   $226.73   $226.75   $226.70  
  Purchase #2 $224.31   9.578%   $245.7944   $245.79   $245.80   $245.80  
  Purchase #3 $154.82   9.189%   $169.0464   $169.05   $169.05   $169.00  
  Purchase #4 $149.38   10.263%   $164.7109   $164.71   $164.70   $164.70  
  Purchase #5 $14.28   7.556%   $15.359   $15.36   $15.35   $15.40  
  Purchase #6 $175.39   6.147%   $186.1712   $186.17   $186.15   $186.20  
  Purchase #7 $143.45   11.842%   $160.4373   $160.44   $160.45   $160.40  
  7 purchase totals = $1,070.01       $1,168.2533   $1,168.25   $1,168.25   $1,168.20