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 $84.62   12.244%   $94.9809   $94.98   $95.00   $95.00  
  Purchase #2 $79.42   5.637%   $83.8969   $83.90   $83.90   $83.90  
  Purchase #3 $136.56   11.485%   $152.2439   $152.24   $152.25   $152.20  
  Purchase #4 $247.36   5.457%   $260.8584   $260.86   $260.85   $260.90  
  Purchase #5 $28.88   10.865%   $32.0178   $32.02   $32.00   $32.00  
  Purchase #6 $229.78   13.128%   $259.9455   $259.95   $259.95   $259.90  
  Purchase #7 $204.50   5.203%   $215.1401   $215.14   $215.15   $215.10  
  7 purchase totals = $1,011.12       $1,099.0835   $1,099.09   $1,099.10   $1,099.00