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	$150.59	5.325%	$158.6089	$158.61	$158.60	$158.60
Purchase #2	$139.27	5.673%	$147.1708	$147.17	$147.15	$147.20
Purchase #3	$151.28	7.425%	$162.5125	$162.51	$162.50	$162.50
Purchase #4	$146.73	3.196%	$151.4195	$151.42	$151.40	$151.40
Purchase #5	$236.86	12.525%	$266.5267	$266.53	$266.55	$266.50
Purchase #6	$180.54	10.733%	$199.9174	$199.92	$199.90	$199.90
Purchase #7	$205.44	5.732%	$217.2158	$217.22	$217.20	$217.20
7 purchase totals =	$1,210.71		$1,303.3716	$1,303.38	$1,303.30	$1,303.30