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 $58.63   11.691%   $65.4844   $65.48   $65.50   $65.50  
  Purchase #2 $93.97   11.340%   $104.6262   $104.63   $104.65   $104.60  
  Purchase #3 $199.29   10.549%   $220.3131   $220.31   $220.30   $220.30  
  Purchase #4 $236.54   5.283%   $249.0364   $249.04   $249.05   $249.00  
  Purchase #5 $34.47   3.196%   $35.5717   $35.57   $35.55   $35.60  
  Purchase #6 $234.89   3.244%   $242.5098   $242.51   $242.50   $242.50  
  Purchase #7 $224.43   4.536%   $234.6101   $234.61   $234.60   $234.60  
  7 purchase totals = $1,082.22       $1,152.1517   $1,152.15   $1,152.15   $1,152.10