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	$101.36	9.793%	$111.2862	$111.29	$111.30	$111.30
Purchase #2	$155.91	3.563%	$161.4651	$161.47	$161.45	$161.50
Purchase #3	$199.90	8.383%	$216.6576	$216.66	$216.65	$216.70
Purchase #4	$190.40	4.105%	$198.2159	$198.22	$198.20	$198.20
Purchase #5	$152.75	8.226%	$165.3152	$165.32	$165.30	$165.30
Purchase #6	$11.54	8.470%	$12.5174	$12.52	$12.50	$12.50
Purchase #7	$176.55	5.294%	$185.8966	$185.90	$185.90	$185.90
7 purchase totals =	$988.41		$1,051.3540	$1,051.38	$1,051.30	$1,051.40