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 $209.42   3.608%   $216.9759   $216.98   $217.00   $217.00  
  Purchase #2 $43.54   8.532%   $47.2548   $47.25   $47.25   $47.30  
  Purchase #3 $209.91   6.507%   $223.5688   $223.57   $223.55   $223.60  
  Purchase #4 $244.25   13.216%   $276.5301   $276.53   $276.55   $276.50  
  Purchase #5 $72.82   3.142%   $75.108   $75.11   $75.10   $75.10  
  Purchase #6 $193.43   13.206%   $218.9744   $218.97   $218.95   $219.00  
  Purchase #7 $172.57   11.836%   $192.9954   $193.00   $193.00   $193.00  
  7 purchase totals = $1,145.94       $1,251.4074   $1,251.41   $1,251.40   $1,251.50