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 $212.95   11.166%   $236.728   $236.73   $236.75   $236.70  
  Purchase #2 $208.47   8.874%   $226.9696   $226.97   $226.95   $227.00  
  Purchase #3 $168.62   3.304%   $174.1912   $174.19   $174.20   $174.20  
  Purchase #4 $30.63   9.347%   $33.493   $33.49   $33.50   $33.50  
  Purchase #5 $67.35   10.865%   $74.6676   $74.67   $74.65   $74.70  
  Purchase #6 $143.68   11.622%   $160.3785   $160.38   $160.40   $160.40  
  Purchase #7 $138.35   13.354%   $156.8253   $156.83   $156.85   $156.80  
  7 purchase totals = $970.05       $1,063.2532   $1,063.26   $1,063.30   $1,063.30