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 $32.63   4.802%   $34.1969   $34.20   $34.20   $34.20  
  Purchase #2 $214.74   5.854%   $227.3109   $227.31   $227.30   $227.30  
  Purchase #3 $119.71   5.779%   $126.628   $126.63   $126.65   $126.60  
  Purchase #4 $242.27   7.455%   $260.3312   $260.33   $260.35   $260.30  
  Purchase #5 $210.88   8.729%   $229.2877   $229.29   $229.30   $229.30  
  Purchase #6 $235.88   12.687%   $265.8061   $265.81   $265.80   $265.80  
  Purchase #7 $60.41   4.205%   $62.9502   $62.95   $62.95   $63.00  
  7 purchase totals = $1,116.52       $1,206.5110   $1,206.52   $1,206.55   $1,206.50