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 $207.26   8.516%   $224.9103   $224.91   $224.90   $224.90  
  Purchase #2 $119.49   5.143%   $125.6354   $125.64   $125.65   $125.60  
  Purchase #3 $188.98   7.595%   $203.333   $203.33   $203.35   $203.30  
  Purchase #4 $209.84   6.838%   $224.1889   $224.19   $224.20   $224.20  
  Purchase #5 $159.37   6.759%   $170.1418   $170.14   $170.15   $170.10  
  Purchase #6 $227.37   7.531%   $244.4932   $244.49   $244.50   $244.50  
  Purchase #7 $16.36   10.196%   $18.0281   $18.03   $18.05   $18.00  
  7 purchase totals = $1,128.67       $1,210.7307   $1,210.73   $1,210.80   $1,210.60