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 $86.39   8.777%   $93.9725   $93.97   $93.95   $94.00  
  Purchase #2 $233.47   4.844%   $244.7793   $244.78   $244.80   $244.80  
  Purchase #3 $236.95   6.567%   $252.5105   $252.51   $252.50   $252.50  
  Purchase #4 $180.38   7.850%   $194.5398   $194.54   $194.55   $194.50  
  Purchase #5 $169.92   3.133%   $175.2436   $175.24   $175.25   $175.20  
  Purchase #6 $52.83   13.561%   $59.9943   $59.99   $60.00   $60.00  
  Purchase #7 $243.62   5.199%   $256.2858   $256.29   $256.30   $256.30  
  7 purchase totals = $1,203.56       $1,277.3258   $1,277.32   $1,277.35   $1,277.30