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	$197.89	3.323%	$204.4659	$204.47	$204.45	$204.50
Purchase #2	$177.33	10.713%	$196.3274	$196.33	$196.35	$196.30
Purchase #3	$87.34	3.852%	$90.7043	$90.70	$90.70	$90.70
Purchase #4	$192.37	12.669%	$216.7414	$216.74	$216.75	$216.70
Purchase #5	$158.94	4.203%	$165.6202	$165.62	$165.60	$165.60
Purchase #6	$46.58	13.849%	$53.0309	$53.03	$53.05	$53.00
Purchase #7	$64.36	3.106%	$66.359	$66.36	$66.35	$66.40
7 purchase totals =	$924.81		$993.2491	$993.25	$993.25	$993.20