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 $41.68   11.743%   $46.5745   $46.57   $46.55   $46.60  
  Purchase #2 $224.81   4.247%   $234.3577   $234.36   $234.35   $234.40  
  Purchase #3 $152.78   8.750%   $166.1483   $166.15   $166.15   $166.10  
  Purchase #4 $39.48   10.580%   $43.657   $43.66   $43.65   $43.70  
  Purchase #5 $89.43   5.317%   $94.185   $94.19   $94.20   $94.20  
  Purchase #6 $75.37   10.319%   $83.1474   $83.15   $83.15   $83.10  
  Purchase #7 $244.89   4.523%   $255.9664   $255.97   $255.95   $256.00  
  7 purchase totals = $868.44       $924.0363   $924.05   $924.00   $924.10