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	$57.51	4.858%	$60.3038	$60.30	$60.30	$60.30
Purchase #2	$52.48	13.791%	$59.7175	$59.72	$59.70	$59.70
Purchase #3	$214.62	8.763%	$233.4272	$233.43	$233.45	$233.40
Purchase #4	$231.57	4.296%	$241.5182	$241.52	$241.50	$241.50
Purchase #5	$209.80	12.565%	$236.1614	$236.16	$236.15	$236.20
Purchase #6	$168.85	11.580%	$188.4028	$188.40	$188.40	$188.40
Purchase #7	$130.84	10.647%	$144.7705	$144.77	$144.75	$144.80
7 purchase totals =	$1,065.67		$1,164.3014	$1,164.30	$1,164.25	$1,164.30