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 $86.73   10.573%   $95.9   $95.90   $95.90   $95.90  
  Purchase #2 $247.89   3.135%   $255.6614   $255.66   $255.65   $255.70  
  Purchase #3 $27.78   4.755%   $29.1009   $29.10   $29.10   $29.10  
  Purchase #4 $242.60   4.553%   $253.6456   $253.65   $253.65   $253.60  
  Purchase #5 $168.31   8.723%   $182.9917   $182.99   $183.00   $183.00  
  Purchase #6 $52.81   13.833%   $60.1152   $60.12   $60.10   $60.10  
  Purchase #7 $46.61   7.871%   $50.2787   $50.28   $50.30   $50.30  
  7 purchase totals = $872.73       $927.6935   $927.70   $927.70   $927.70