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	$221.90	5.745%	$234.6482	$234.65	$234.65	$234.60
Purchase #2	$79.47	3.561%	$82.2999	$82.30	$82.30	$82.30
Purchase #3	$97.29	6.303%	$103.4222	$103.42	$103.40	$103.40
Purchase #4	$146.58	7.849%	$158.0851	$158.09	$158.10	$158.10
Purchase #5	$186.70	9.852%	$205.0937	$205.09	$205.10	$205.10
Purchase #6	$169.29	5.779%	$179.0733	$179.07	$179.05	$179.10
Purchase #7	$172.77	9.640%	$189.425	$189.43	$189.45	$189.40
7 purchase totals =	$1,074.00		$1,152.0474	$1,152.05	$1,152.05	$1,152.00