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 $84.34   12.592%   $94.9601   $94.96   $94.95   $95.00  
  Purchase #2 $145.94   5.679%   $154.2279   $154.23   $154.25   $154.20  
  Purchase #3 $154.95   8.726%   $168.4709   $168.47   $168.45   $168.50  
  Purchase #4 $101.43   3.656%   $105.1383   $105.14   $105.15   $105.10  
  Purchase #5 $32.50   11.863%   $36.3555   $36.36   $36.35   $36.40  
  Purchase #6 $140.96   10.773%   $156.1456   $156.15   $156.15   $156.10  
  Purchase #7 $206.57   13.771%   $235.0168   $235.02   $235.00   $235.00  
  7 purchase totals = $866.69       $950.3151   $950.33   $950.30   $950.30