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	$204.31	6.198%	$216.9731	$216.97	$216.95	$217.00
Purchase #2	$172.99	7.298%	$185.6148	$185.61	$185.60	$185.60
Purchase #3	$136.90	11.399%	$152.5052	$152.51	$152.50	$152.50
Purchase #4	$150.78	4.293%	$157.253	$157.25	$157.25	$157.30
Purchase #5	$214.27	3.242%	$221.2166	$221.22	$221.20	$221.20
Purchase #6	$244.60	8.319%	$264.9483	$264.95	$264.95	$264.90
Purchase #7	$135.76	10.788%	$150.4058	$150.41	$150.40	$150.40
7 purchase totals =	$1,259.61		$1,348.9168	$1,348.92	$1,348.85	$1,348.90