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 $58.99   5.195%   $62.0545   $62.05   $62.05   $62.10  
  Purchase #2 $51.53   5.763%   $54.4997   $54.50   $54.50   $54.50  
  Purchase #3 $201.74   5.656%   $213.1504   $213.15   $213.15   $213.20  
  Purchase #4 $137.67   5.161%   $144.7751   $144.78   $144.80   $144.80  
  Purchase #5 $188.56   4.727%   $197.4732   $197.47   $197.45   $197.50  
  Purchase #6 $216.26   5.211%   $227.5293   $227.53   $227.55   $227.50  
  Purchase #7 $31.43   10.636%   $34.7729   $34.77   $34.75   $34.80  
  7 purchase totals = $886.18       $934.2551   $934.25   $934.25   $934.40