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 $112.29   5.650%   $118.6344   $118.63   $118.65   $118.60  
  Purchase #2 $195.30   7.629%   $210.1994   $210.20   $210.20   $210.20  
  Purchase #3 $31.27   8.602%   $33.9598   $33.96   $33.95   $34.00  
  Purchase #4 $82.62   6.832%   $88.2646   $88.26   $88.25   $88.30  
  Purchase #5 $216.35   9.487%   $236.8751   $236.88   $236.90   $236.90  
  Purchase #6 $91.73   10.784%   $101.6222   $101.62   $101.60   $101.60  
  Purchase #7 $49.56   8.404%   $53.725   $53.73   $53.75   $53.70  
  7 purchase totals = $779.12       $843.2805   $843.28   $843.30   $843.30