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 $91.78   3.566%   $95.0529   $95.05   $95.05   $95.10  
  Purchase #2 $69.44   3.554%   $71.9079   $71.91   $71.90   $71.90  
  Purchase #3 $129.49   3.589%   $134.1374   $134.14   $134.15   $134.10  
  Purchase #4 $201.79   12.420%   $226.8523   $226.85   $226.85   $226.90  
  Purchase #5 $82.62   4.245%   $86.1272   $86.13   $86.15   $86.10  
  Purchase #6 $120.87   7.168%   $129.534   $129.53   $129.55   $129.50  
  Purchase #7 $184.42   13.710%   $209.704   $209.70   $209.70   $209.70  
  7 purchase totals = $880.41       $953.3157   $953.31   $953.35   $953.30