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	$108.61	4.679%	$113.6919	$113.69	$113.70	$113.70
Purchase #2	$187.75	13.273%	$212.6701	$212.67	$212.65	$212.70
Purchase #3	$143.92	3.696%	$149.2393	$149.24	$149.25	$149.20
Purchase #4	$48.59	10.566%	$53.724	$53.72	$53.70	$53.70
Purchase #5	$31.60	4.733%	$33.0956	$33.10	$33.10	$33.10
Purchase #6	$119.93	6.654%	$127.9101	$127.91	$127.90	$127.90
Purchase #7	$91.75	13.104%	$103.7729	$103.77	$103.75	$103.80
7 purchase totals =	$732.15		$794.1039	$794.10	$794.05	$794.10