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 $182.84   6.747%   $195.1762   $195.18   $195.20   $195.20  
  Purchase #2 $173.36   5.470%   $182.8428   $182.84   $182.85   $182.80  
  Purchase #3 $244.91   11.304%   $272.5946   $272.59   $272.60   $272.60  
  Purchase #4 $220.87   6.628%   $235.5093   $235.51   $235.50   $235.50  
  Purchase #5 $190.70   4.618%   $199.5065   $199.51   $199.50   $199.50  
  Purchase #6 $143.99   11.342%   $160.3213   $160.32   $160.30   $160.30  
  Purchase #7 $206.56   13.811%   $235.088   $235.09   $235.10   $235.10  
  7 purchase totals = $1,363.23       $1,481.0387   $1,481.04   $1,481.05   $1,481.00