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 $214.93   13.688%   $244.3496   $244.35   $244.35   $244.30  
  Purchase #2 $181.42   6.848%   $193.8436   $193.84   $193.85   $193.80  
  Purchase #3 $102.87   5.507%   $108.5351   $108.54   $108.55   $108.50  
  Purchase #4 $69.58   5.830%   $73.6365   $73.64   $73.65   $73.60  
  Purchase #5 $105.29   9.248%   $115.0272   $115.03   $115.05   $115.00  
  Purchase #6 $203.93   9.291%   $222.8771   $222.88   $222.90   $222.90  
  Purchase #7 $103.97   11.639%   $116.0711   $116.07   $116.05   $116.10  
  7 purchase totals = $981.99       $1,074.3402   $1,074.35   $1,074.40   $1,074.20