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 $67.37   12.742%   $75.9543   $75.95   $75.95   $76.00  
  Purchase #2 $138.56   10.239%   $152.7472   $152.75   $152.75   $152.70  
  Purchase #3 $214.57   11.516%   $239.2799   $239.28   $239.30   $239.30  
  Purchase #4 $223.54   9.613%   $245.0289   $245.03   $245.05   $245.00  
  Purchase #5 $118.56   3.674%   $122.9159   $122.92   $122.90   $122.90  
  Purchase #6 $244.66   13.698%   $278.1735   $278.17   $278.15   $278.20  
  Purchase #7 $104.57   6.661%   $111.5354   $111.54   $111.55   $111.50  
  7 purchase totals = $1,111.83       $1,225.6351   $1,225.64   $1,225.65   $1,225.60