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 $90.77   4.633%   $94.9754   $94.98   $95.00   $95.00  
  Purchase #2 $128.25   12.146%   $143.8272   $143.83   $143.85   $143.80  
  Purchase #3 $125.73   5.131%   $132.1812   $132.18   $132.20   $132.20  
  Purchase #4 $81.34   13.636%   $92.4315   $92.43   $92.45   $92.40  
  Purchase #5 $83.34   9.516%   $91.2706   $91.27   $91.25   $91.30  
  Purchase #6 $130.29   13.477%   $147.8492   $147.85   $147.85   $147.80  
  Purchase #7 $46.97   5.619%   $49.6092   $49.61   $49.60   $49.60  
  7 purchase totals = $686.69       $752.1443   $752.15   $752.20   $752.10