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	$120.92	7.858%	$130.4219	$130.42	$130.40	$130.40
Purchase #2	$91.78	10.642%	$101.5472	$101.55	$101.55	$101.50
Purchase #3	$115.44	10.584%	$127.6582	$127.66	$127.65	$127.70
Purchase #4	$20.31	10.862%	$22.5161	$22.52	$22.50	$22.50
Purchase #5	$200.65	5.733%	$212.1533	$212.15	$212.15	$212.20
Purchase #6	$196.76	7.401%	$211.3222	$211.32	$211.30	$211.30
Purchase #7	$205.29	4.517%	$214.5629	$214.56	$214.55	$214.60
7 purchase totals =	$951.15		$1,020.1818	$1,020.18	$1,020.10	$1,020.20