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	$102.56	6.559%	$109.2869	$109.29	$109.30	$109.30
Purchase #2	$145.80	3.215%	$150.4875	$150.49	$150.50	$150.50
Purchase #3	$182.62	5.307%	$192.3116	$192.31	$192.30	$192.30
Purchase #4	$55.47	4.109%	$57.7493	$57.75	$57.75	$57.70
Purchase #5	$130.61	11.866%	$146.1082	$146.11	$146.10	$146.10
Purchase #6	$61.81	8.103%	$66.8185	$66.82	$66.80	$66.80
Purchase #7	$156.52	9.733%	$171.7541	$171.75	$171.75	$171.80
7 purchase totals =	$835.39		$894.5161	$894.52	$894.50	$894.50