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 $183.62   6.343%   $195.267   $195.27   $195.25   $195.30  
  Purchase #2 $89.51   6.679%   $95.4884   $95.49   $95.50   $95.50  
  Purchase #3 $44.76   5.401%   $47.1775   $47.18   $47.20   $47.20  
  Purchase #4 $93.27   4.379%   $97.3543   $97.35   $97.35   $97.40  
  Purchase #5 $137.72   3.524%   $142.5733   $142.57   $142.55   $142.60  
  Purchase #6 $66.64   11.676%   $74.4209   $74.42   $74.40   $74.40  
  Purchase #7 $129.42   3.511%   $133.9639   $133.96   $133.95   $134.00  
  7 purchase totals = $744.94       $786.2453   $786.24   $786.20   $786.40