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	$141.40	4.324%	$147.5141	$147.51	$147.50	$147.50
Purchase #2	$231.42	10.476%	$255.6636	$255.66	$255.65	$255.70
Purchase #3	$132.34	10.579%	$146.3402	$146.34	$146.35	$146.30
Purchase #4	$163.43	10.855%	$181.1703	$181.17	$181.15	$181.20
Purchase #5	$223.85	7.480%	$240.594	$240.59	$240.60	$240.60
Purchase #6	$102.72	9.152%	$112.1209	$112.12	$112.10	$112.10
Purchase #7	$250.27	5.821%	$264.8382	$264.84	$264.85	$264.80
7 purchase totals =	$1,245.43		$1,348.2413	$1,348.23	$1,348.20	$1,348.20