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	$60.97	3.184%	$62.9113	$62.91	$62.90	$62.90
Purchase #2	$152.50	10.829%	$169.0142	$169.01	$169.00	$169.00
Purchase #3	$246.88	10.806%	$273.5579	$273.56	$273.55	$273.60
Purchase #4	$75.27	3.340%	$77.784	$77.78	$77.80	$77.80
Purchase #5	$211.59	10.286%	$233.3541	$233.35	$233.35	$233.40
Purchase #6	$176.99	7.602%	$190.4448	$190.44	$190.45	$190.40
Purchase #7	$8.69	3.105%	$8.9598	$8.96	$8.95	$9.00
7 purchase totals =	$932.89		$1,016.0261	$1,016.01	$1,016.00	$1,016.10