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	$176.53	7.852%	$190.3911	$190.39	$190.40	$190.40
Purchase #2	$162.35	13.520%	$184.2997	$184.30	$184.30	$184.30
Purchase #3	$50.54	6.583%	$53.867	$53.87	$53.85	$53.90
Purchase #4	$127.98	7.149%	$137.1293	$137.13	$137.15	$137.10
Purchase #5	$159.70	6.221%	$169.6349	$169.63	$169.65	$169.60
Purchase #6	$11.47	9.625%	$12.574	$12.57	$12.55	$12.60
Purchase #7	$71.52	9.426%	$78.2615	$78.26	$78.25	$78.30
7 purchase totals =	$760.09		$826.1575	$826.15	$826.15	$826.20