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 $72.59   3.820%   $75.3629   $75.36   $75.35   $75.40  
  Purchase #2 $229.81   13.453%   $260.7263   $260.73   $260.75   $260.70  
  Purchase #3 $53.29   8.673%   $57.9118   $57.91   $57.90   $57.90  
  Purchase #4 $119.31   3.627%   $123.6374   $123.64   $123.65   $123.60  
  Purchase #5 $57.75   11.217%   $64.2278   $64.23   $64.25   $64.20  
  Purchase #6 $203.92   10.563%   $225.4601   $225.46   $225.45   $225.50  
  Purchase #7 $136.60   4.655%   $142.9587   $142.96   $142.95   $143.00  
  7 purchase totals = $873.27       $950.2850   $950.29   $950.30   $950.30