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 $92.74   3.366%   $95.8616   $95.86   $95.85   $95.90  
  Purchase #2 $222.47   11.368%   $247.7604   $247.76   $247.75   $247.80  
  Purchase #3 $55.95   8.348%   $60.6207   $60.62   $60.60   $60.60  
  Purchase #4 $227.49   7.794%   $245.2206   $245.22   $245.20   $245.20  
  Purchase #5 $129.66   9.151%   $141.5252   $141.53   $141.55   $141.50  
  Purchase #6 $111.41   13.858%   $126.8492   $126.85   $126.85   $126.80  
  Purchase #7 $149.98   13.233%   $169.8269   $169.83   $169.85   $169.80  
  7 purchase totals = $989.70       $1,087.6646   $1,087.67   $1,087.65   $1,087.60