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	$48.46	10.271%	$53.4373	$53.44	$53.45	$53.40
Purchase #2	$206.80	12.795%	$233.2601	$233.26	$233.25	$233.30
Purchase #3	$111.91	12.733%	$126.1595	$126.16	$126.15	$126.20
Purchase #4	$247.49	3.218%	$255.4542	$255.45	$255.45	$255.50
Purchase #5	$151.28	9.235%	$165.2507	$165.25	$165.25	$165.30
Purchase #6	$238.58	13.616%	$271.0651	$271.07	$271.05	$271.10
Purchase #7	$171.36	9.859%	$188.2544	$188.25	$188.25	$188.30
7 purchase totals =	$1,175.88		$1,292.8813	$1,292.88	$1,292.85	$1,293.10