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 $209.71   3.731%   $217.5343   $217.53   $217.55   $217.50  
  Purchase #2 $206.84   13.612%   $234.9951   $235.00   $235.00   $235.00  
  Purchase #3 $76.43   5.220%   $80.4196   $80.42   $80.40   $80.40  
  Purchase #4 $32.70   5.105%   $34.3693   $34.37   $34.35   $34.40  
  Purchase #5 $81.36   6.231%   $86.4295   $86.43   $86.45   $86.40  
  Purchase #6 $145.98   11.824%   $163.2407   $163.24   $163.25   $163.20  
  Purchase #7 $122.44   8.678%   $133.0653   $133.07   $133.05   $133.10  
  7 purchase totals = $875.46       $950.0538   $950.06   $950.05   $950.00