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 $60.48   4.460%   $63.1774   $63.18   $63.20   $63.20  
  Purchase #2 $244.38   3.406%   $252.7036   $252.70   $252.70   $252.70  
  Purchase #3 $59.31   11.181%   $65.9415   $65.94   $65.95   $65.90  
  Purchase #4 $55.89   10.512%   $61.7652   $61.77   $61.75   $61.80  
  Purchase #5 $36.76   7.422%   $39.4883   $39.49   $39.50   $39.50  
  Purchase #6 $160.76   7.704%   $173.145   $173.15   $173.15   $173.10  
  Purchase #7 $68.41   7.358%   $73.4436   $73.44   $73.45   $73.40  
  7 purchase totals = $685.99       $729.6646   $729.67   $729.70   $729.60