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 $13.47   5.858%   $14.2591   $14.26   $14.25   $14.30  
  Purchase #2 $212.33   13.151%   $240.2535   $240.25   $240.25   $240.30  
  Purchase #3 $204.76   11.181%   $227.6542   $227.65   $227.65   $227.70  
  Purchase #4 $12.72   11.673%   $14.2048   $14.20   $14.20   $14.20  
  Purchase #5 $62.47   11.496%   $69.6516   $69.65   $69.65   $69.70  
  Purchase #6 $132.27   9.810%   $145.2457   $145.25   $145.25   $145.20  
  Purchase #7 $238.96   4.191%   $248.9748   $248.97   $248.95   $249.00  
  7 purchase totals = $876.98       $960.2437   $960.23   $960.20   $960.40