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 $215.60   13.263%   $244.195   $244.20   $244.20   $244.20  
  Purchase #2 $13.65   10.110%   $15.03   $15.03   $15.05   $15.00  
  Purchase #3 $51.46   10.300%   $56.7604   $56.76   $56.75   $56.80  
  Purchase #4 $190.59   7.346%   $204.5907   $204.59   $204.60   $204.60  
  Purchase #5 $66.47   11.179%   $73.9007   $73.90   $73.90   $73.90  
  Purchase #6 $115.58   9.625%   $126.7046   $126.70   $126.70   $126.70  
  Purchase #7 $215.42   6.384%   $229.1724   $229.17   $229.15   $229.20  
  7 purchase totals = $868.77       $950.3538   $950.35   $950.35   $950.40