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	$235.79	7.184%	$252.7292	$252.73	$252.75	$252.70
Purchase #2	$204.44	4.842%	$214.339	$214.34	$214.35	$214.30
Purchase #3	$59.62	11.738%	$66.6182	$66.62	$66.60	$66.60
Purchase #4	$172.59	7.452%	$185.4514	$185.45	$185.45	$185.50
Purchase #5	$38.54	4.580%	$40.3051	$40.31	$40.30	$40.30
Purchase #6	$157.29	11.360%	$175.1581	$175.16	$175.15	$175.20
Purchase #7	$243.31	8.731%	$264.5534	$264.55	$264.55	$264.60
7 purchase totals =	$1,111.58		$1,199.1544	$1,199.16	$1,199.15	$1,199.20