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 $212.35   5.487%   $224.0016   $224.00   $224.00   $224.00  
  Purchase #2 $91.33   4.455%   $95.3988   $95.40   $95.40   $95.40  
  Purchase #3 $89.62   6.474%   $95.422   $95.42   $95.40   $95.40  
  Purchase #4 $194.41   5.304%   $204.7215   $204.72   $204.70   $204.70  
  Purchase #5 $24.55   13.419%   $27.8444   $27.84   $27.85   $27.80  
  Purchase #6 $187.55   4.403%   $195.8078   $195.81   $195.80   $195.80  
  Purchase #7 $68.96   5.775%   $72.9424   $72.94   $72.95   $72.90  
  7 purchase totals = $868.77       $916.1385   $916.13   $916.10   $916.00