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 $66.65   3.458%   $68.9548   $68.95   $68.95   $69.00  
  Purchase #2 $215.70   5.340%   $227.2184   $227.22   $227.20   $227.20  
  Purchase #3 $186.73   3.111%   $192.5392   $192.54   $192.55   $192.50  
  Purchase #4 $210.86   6.515%   $224.5975   $224.60   $224.60   $224.60  
  Purchase #5 $223.48   11.818%   $249.8909   $249.89   $249.90   $249.90  
  Purchase #6 $187.97   13.236%   $212.8497   $212.85   $212.85   $212.80  
  Purchase #7 $173.84   8.126%   $187.9662   $187.97   $187.95   $188.00  
  7 purchase totals = $1,265.23       $1,364.0167   $1,364.02   $1,364.00   $1,364.00