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 $167.80   5.664%   $177.3042   $177.30   $177.30   $177.30  
  Purchase #2 $244.33   4.673%   $255.7475   $255.75   $255.75   $255.70  
  Purchase #3 $200.85   6.429%   $213.7626   $213.76   $213.75   $213.80  
  Purchase #4 $95.45   4.591%   $99.8321   $99.83   $99.85   $99.80  
  Purchase #5 $155.45   8.183%   $168.1705   $168.17   $168.15   $168.20  
  Purchase #6 $19.43   9.134%   $21.2047   $21.20   $21.20   $21.20  
  Purchase #7 $83.44   6.166%   $88.5849   $88.58   $88.60   $88.60  
  7 purchase totals = $966.75       $1,024.6065   $1,024.59   $1,024.60   $1,024.60