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	$176.39	12.399%	$198.2606	$198.26	$198.25	$198.30
Purchase #2	$107.64	10.413%	$118.8486	$118.85	$118.85	$118.80
Purchase #3	$81.49	12.382%	$91.5801	$91.58	$91.60	$91.60
Purchase #4	$84.31	7.584%	$90.7041	$90.70	$90.70	$90.70
Purchase #5	$151.28	10.858%	$167.706	$167.71	$167.70	$167.70
Purchase #6	$124.95	4.139%	$130.1217	$130.12	$130.10	$130.10
Purchase #7	$79.28	12.687%	$89.3383	$89.34	$89.35	$89.30
7 purchase totals =	$805.34		$886.5594	$886.56	$886.55	$886.50