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	$64.49	8.124%	$69.7292	$69.73	$69.75	$69.70
Purchase #2	$92.30	9.250%	$100.8378	$100.84	$100.85	$100.80
Purchase #3	$123.33	3.492%	$127.6367	$127.64	$127.65	$127.60
Purchase #4	$51.58	3.548%	$53.4101	$53.41	$53.40	$53.40
Purchase #5	$17.94	3.266%	$18.5259	$18.53	$18.55	$18.50
Purchase #6	$36.69	10.174%	$40.4228	$40.42	$40.40	$40.40
Purchase #7	$54.44	11.594%	$60.7518	$60.75	$60.75	$60.80
7 purchase totals =	$440.77		$471.3143	$471.32	$471.35	$471.20