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 $182.38   10.559%   $201.6375   $201.64   $201.65   $201.60  
  Purchase #2 $233.70   12.452%   $262.8003   $262.80   $262.80   $262.80  
  Purchase #3 $143.80   10.401%   $158.7566   $158.76   $158.75   $158.80  
  Purchase #4 $207.91   5.340%   $219.0124   $219.01   $219.00   $219.00  
  Purchase #5 $215.73   13.588%   $245.0434   $245.04   $245.05   $245.00  
  Purchase #6 $186.38   5.829%   $197.2441   $197.24   $197.25   $197.20  
  Purchase #7 $49.37   4.335%   $51.5102   $51.51   $51.50   $51.50  
  7 purchase totals = $1,219.27       $1,336.0045   $1,336.00   $1,336.00   $1,335.90