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 $59.33   5.241%   $62.4395   $62.44   $62.45   $62.40  
  Purchase #2 $112.39   10.773%   $124.4978   $124.50   $124.50   $124.50  
  Purchase #3 $199.65   13.823%   $227.2476   $227.25   $227.25   $227.20  
  Purchase #4 $107.83   13.574%   $122.4668   $122.47   $122.45   $122.50  
  Purchase #5 $152.45   5.249%   $160.4521   $160.45   $160.45   $160.50  
  Purchase #6 $108.97   5.567%   $115.0364   $115.04   $115.05   $115.00  
  Purchase #7 $44.52   12.341%   $50.0142   $50.01   $50.00   $50.00  
  7 purchase totals = $785.14       $862.1544   $862.16   $862.15   $862.10