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	$130.70	13.719%	$148.6307	$148.63	$148.65	$148.60
Purchase #2	$28.68	9.158%	$31.3065	$31.31	$31.30	$31.30
Purchase #3	$148.34	11.397%	$165.2463	$165.25	$165.25	$165.20
Purchase #4	$148.46	3.643%	$153.8684	$153.87	$153.85	$153.90
Purchase #5	$244.31	11.390%	$272.1369	$272.14	$272.15	$272.10
Purchase #6	$119.91	6.478%	$127.6778	$127.68	$127.70	$127.70
Purchase #7	$248.48	12.494%	$279.5251	$279.53	$279.55	$279.50
7 purchase totals =	$1,068.88		$1,178.3917	$1,178.41	$1,178.45	$1,178.30