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	$150.54	9.836%	$165.3471	$165.35	$165.35	$165.30
Purchase #2	$26.51	5.817%	$28.0521	$28.05	$28.05	$28.10
Purchase #3	$111.86	13.814%	$127.3123	$127.31	$127.30	$127.30
Purchase #4	$28.65	3.648%	$29.6952	$29.70	$29.70	$29.70
Purchase #5	$121.43	8.485%	$131.7333	$131.73	$131.75	$131.70
Purchase #6	$100.31	13.789%	$114.1417	$114.14	$114.15	$114.10
Purchase #7	$84.27	6.406%	$89.6683	$89.67	$89.65	$89.70
7 purchase totals =	$623.57		$685.9500	$685.95	$685.95	$685.90