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	$177.39	10.820%	$196.5836	$196.58	$196.60	$196.60
Purchase #2	$228.51	13.656%	$259.7153	$259.72	$259.70	$259.70
Purchase #3	$64.65	11.478%	$72.0705	$72.07	$72.05	$72.10
Purchase #4	$211.26	6.823%	$225.6743	$225.67	$225.65	$225.70
Purchase #5	$147.28	12.391%	$165.5295	$165.53	$165.55	$165.50
Purchase #6	$230.99	10.165%	$254.4701	$254.47	$254.45	$254.50
Purchase #7	$240.86	9.399%	$263.4984	$263.50	$263.50	$263.50
7 purchase totals =	$1,300.94		$1,437.5417	$1,437.54	$1,437.50	$1,437.60