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 $55.32   13.326%   $62.6919   $62.69   $62.70   $62.70  
  Purchase #2 $195.56   13.556%   $222.0701   $222.07   $222.05   $222.10  
  Purchase #3 $123.73   6.843%   $132.1968   $132.20   $132.20   $132.20  
  Purchase #4 $56.63   7.661%   $60.9684   $60.97   $60.95   $61.00  
  Purchase #5 $244.41   8.186%   $264.4174   $264.42   $264.40   $264.40  
  Purchase #6 $149.49   13.198%   $169.2197   $169.22   $169.20   $169.20  
  Purchase #7 $139.50   5.853%   $147.6649   $147.66   $147.65   $147.70  
  7 purchase totals = $964.64       $1,059.2292   $1,059.23   $1,059.15   $1,059.30