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	$87.83	4.675%	$91.9361	$91.94	$91.95	$91.90
Purchase #2	$60.68	5.552%	$64.049	$64.05	$64.05	$64.00
Purchase #3	$165.60	13.668%	$188.2342	$188.23	$188.25	$188.20
Purchase #4	$48.59	11.863%	$54.3542	$54.35	$54.35	$54.40
Purchase #5	$50.65	7.821%	$54.6113	$54.61	$54.60	$54.60
Purchase #6	$57.39	3.860%	$59.6053	$59.61	$59.60	$59.60
Purchase #7	$106.97	10.506%	$118.2083	$118.21	$118.20	$118.20
7 purchase totals =	$577.71		$630.9984	$631.00	$631.00	$630.90