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 $88.69   7.526%   $95.3648   $95.36   $95.35   $95.40  
  Purchase #2 $238.99   5.235%   $251.5011   $251.50   $251.50   $251.50  
  Purchase #3 $59.38   4.187%   $61.8662   $61.87   $61.85   $61.90  
  Purchase #4 $157.75   12.348%   $177.229   $177.23   $177.25   $177.20  
  Purchase #5 $213.48   8.536%   $231.7027   $231.70   $231.70   $231.70  
  Purchase #6 $240.66   6.497%   $256.2957   $256.30   $256.30   $256.30  
  Purchase #7 $216.93   13.295%   $245.7708   $245.77   $245.75   $245.80  
  7 purchase totals = $1,215.88       $1,319.7303   $1,319.73   $1,319.70   $1,319.80