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 $69.41   5.415%   $73.1686   $73.17   $73.15   $73.20  
  Purchase #2 $221.38   4.792%   $231.9885   $231.99   $232.00   $232.00  
  Purchase #3 $244.79   4.665%   $256.2095   $256.21   $256.20   $256.20  
  Purchase #4 $114.76   6.224%   $121.9027   $121.90   $121.90   $121.90  
  Purchase #5 $103.35   11.290%   $115.0182   $115.02   $115.00   $115.00  
  Purchase #6 $41.47   9.113%   $45.2492   $45.25   $45.25   $45.20  
  Purchase #7 $124.82   4.851%   $130.875   $130.88   $130.90   $130.90  
  7 purchase totals = $919.98       $974.4117   $974.42   $974.40   $974.40