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	$171.96	5.517%	$181.447	$181.45	$181.45	$181.40
Purchase #2	$11.38	7.594%	$12.2442	$12.24	$12.25	$12.20
Purchase #3	$250.66	11.199%	$278.7314	$278.73	$278.75	$278.70
Purchase #4	$50.64	7.370%	$54.3722	$54.37	$54.35	$54.40
Purchase #5	$32.59	7.137%	$34.9159	$34.92	$34.90	$34.90
Purchase #6	$90.94	5.522%	$95.9617	$95.96	$95.95	$96.00
Purchase #7	$235.72	3.843%	$244.7787	$244.78	$244.80	$244.80
7 purchase totals =	$843.89		$902.4511	$902.45	$902.45	$902.40