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 $59.61   5.297%   $62.7675   $62.77   $62.75   $62.80  
  Purchase #2 $229.41   3.669%   $237.8271   $237.83   $237.85   $237.80  
  Purchase #3 $139.87   9.125%   $152.6331   $152.63   $152.65   $152.60  
  Purchase #4 $194.83   7.380%   $209.2085   $209.21   $209.20   $209.20  
  Purchase #5 $29.54   11.770%   $33.0169   $33.02   $33.00   $33.00  
  Purchase #6 $78.53   7.753%   $84.6184   $84.62   $84.60   $84.60  
  Purchase #7 $206.94   3.253%   $213.6718   $213.67   $213.65   $213.70  
  7 purchase totals = $938.73       $993.7433   $993.75   $993.70   $993.70