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 $57.87   7.792%   $62.3792   $62.38   $62.40   $62.40  
  Purchase #2 $150.69   9.299%   $164.7027   $164.70   $164.70   $164.70  
  Purchase #3 $33.26   12.769%   $37.507   $37.51   $37.50   $37.50  
  Purchase #4 $130.73   9.130%   $142.6656   $142.67   $142.65   $142.70  
  Purchase #5 $120.38   4.490%   $125.7851   $125.79   $125.80   $125.80  
  Purchase #6 $23.64   10.735%   $26.1778   $26.18   $26.20   $26.20  
  Purchase #7 $170.41   13.842%   $193.9982   $194.00   $194.00   $194.00  
  7 purchase totals = $686.98       $753.2156   $753.23   $753.25   $753.30