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 $47.33   13.634%   $53.783   $53.78   $53.80   $53.80  
  Purchase #2 $57.38   7.747%   $61.8252   $61.83   $61.85   $61.80  
  Purchase #3 $63.27   9.565%   $69.3218   $69.32   $69.30   $69.30  
  Purchase #4 $67.48   5.707%   $71.3311   $71.33   $71.35   $71.30  
  Purchase #5 $196.57   9.793%   $215.8201   $215.82   $215.80   $215.80  
  Purchase #6 $186.75   8.205%   $202.0728   $202.07   $202.05   $202.10  
  Purchase #7 $233.73   4.744%   $244.8182   $244.82   $244.80   $244.80  
  7 purchase totals = $852.51       $918.9722   $918.97   $918.95   $918.90