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 $218.64   3.609%   $226.5307   $226.53   $226.55   $226.50  
  Purchase #2 $98.94   5.319%   $104.2026   $104.20   $104.20   $104.20  
  Purchase #3 $197.87   11.865%   $221.3473   $221.35   $221.35   $221.30  
  Purchase #4 $22.73   3.537%   $23.534   $23.53   $23.55   $23.50  
  Purchase #5 $223.69   6.104%   $237.344   $237.34   $237.35   $237.30  
  Purchase #6 $236.60   8.341%   $256.3348   $256.33   $256.35   $256.30  
  Purchase #7 $117.75   6.273%   $125.1365   $125.14   $125.15   $125.10  
  7 purchase totals = $1,116.22       $1,194.4299   $1,194.42   $1,194.50   $1,194.20