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 $33.46   11.533%   $37.3189   $37.32   $37.30   $37.30  
  Purchase #2 $104.25   6.163%   $110.6749   $110.67   $110.65   $110.70  
  Purchase #3 $104.39   11.120%   $115.9982   $116.00   $116.00   $116.00  
  Purchase #4 $72.78   4.525%   $76.0733   $76.07   $76.05   $76.10  
  Purchase #5 $5.60   7.267%   $6.007   $6.01   $6.00   $6.00  
  Purchase #6 $195.29   6.718%   $208.4096   $208.41   $208.40   $208.40  
  Purchase #7 $142.65   11.605%   $159.2045   $159.20   $159.20   $159.20  
  7 purchase totals = $658.42       $713.6864   $713.68   $713.60   $713.70