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 $86.81   9.701%   $95.2314   $95.23   $95.25   $95.20  
  Purchase #2 $89.48   3.130%   $92.2807   $92.28   $92.30   $92.30  
  Purchase #3 $241.36   5.817%   $255.3999   $255.40   $255.40   $255.40  
  Purchase #4 $157.75   12.253%   $177.0791   $177.08   $177.10   $177.10  
  Purchase #5 $89.53   10.196%   $98.6585   $98.66   $98.65   $98.70  
  Purchase #6 $41.92   11.286%   $46.6511   $46.65   $46.65   $46.70  
  Purchase #7 $193.50   3.282%   $199.8507   $199.85   $199.85   $199.90  
  7 purchase totals = $900.35       $965.1514   $965.15   $965.20   $965.30