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	$122.79	7.631%	$132.1601	$132.16	$132.15	$132.20
Purchase #2	$76.37	10.362%	$84.2835	$84.28	$84.30	$84.30
Purchase #3	$116.43	5.756%	$123.1317	$123.13	$123.15	$123.10
Purchase #4	$164.77	4.411%	$172.038	$172.04	$172.05	$172.00
Purchase #5	$248.35	12.453%	$279.277	$279.28	$279.30	$279.30
Purchase #6	$127.76	13.422%	$144.9079	$144.91	$144.90	$144.90
Purchase #7	$174.41	9.409%	$190.8202	$190.82	$190.80	$190.80
7 purchase totals =	$1,030.88		$1,126.6184	$1,126.62	$1,126.65	$1,126.60