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 $69.56   8.475%   $75.4552   $75.46   $75.45   $75.50  
  Purchase #2 $131.34   13.202%   $148.6795   $148.68   $148.70   $148.70  
  Purchase #3 $225.69   13.740%   $256.6998   $256.70   $256.70   $256.70  
  Purchase #4 $217.40   6.660%   $231.8788   $231.88   $231.90   $231.90  
  Purchase #5 $15.87   8.211%   $17.1731   $17.17   $17.15   $17.20  
  Purchase #6 $147.45   5.603%   $155.7116   $155.71   $155.70   $155.70  
  Purchase #7 $241.52   10.863%   $267.7563   $267.76   $267.75   $267.80  
  7 purchase totals = $1,048.83       $1,153.3543   $1,153.36   $1,153.35   $1,153.50