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	$180.76	9.369%	$197.6954	$197.70	$197.70	$197.70
Purchase #2	$85.30	4.646%	$89.263	$89.26	$89.25	$89.30
Purchase #3	$250.92	11.362%	$279.4295	$279.43	$279.45	$279.40
Purchase #4	$217.65	6.275%	$231.3075	$231.31	$231.30	$231.30
Purchase #5	$145.32	13.585%	$165.0617	$165.06	$165.05	$165.10
Purchase #6	$89.52	13.611%	$101.7046	$101.70	$101.70	$101.70
Purchase #7	$46.35	9.370%	$50.693	$50.69	$50.70	$50.70
7 purchase totals =	$1,015.82		$1,115.1547	$1,115.15	$1,115.15	$1,115.20