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 $198.61   6.236%   $210.9953   $211.00   $211.00   $211.00  
  Purchase #2 $16.94   13.531%   $19.2322   $19.23   $19.25   $19.20  
  Purchase #3 $185.78   6.628%   $198.0935   $198.09   $198.10   $198.10  
  Purchase #4 $24.49   11.506%   $27.3078   $27.31   $27.30   $27.30  
  Purchase #5 $209.93   8.197%   $227.138   $227.14   $227.15   $227.10  
  Purchase #6 $237.72   6.506%   $253.1861   $253.19   $253.20   $253.20  
  Purchase #7 $150.86   5.385%   $158.9838   $158.98   $159.00   $159.00  
  7 purchase totals = $1,024.33       $1,094.9367   $1,094.94   $1,095.00   $1,094.90