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	$91.53	13.565%	$103.946	$103.95	$103.95	$103.90
Purchase #2	$220.70	13.510%	$250.5166	$250.52	$250.50	$250.50
Purchase #3	$172.60	12.192%	$193.6434	$193.64	$193.65	$193.60
Purchase #4	$116.48	10.825%	$129.089	$129.09	$129.10	$129.10
Purchase #5	$37.28	13.375%	$42.2662	$42.27	$42.25	$42.30
Purchase #6	$100.54	10.542%	$111.1389	$111.14	$111.15	$111.10
Purchase #7	$14.80	10.574%	$16.365	$16.37	$16.35	$16.40
7 purchase totals =	$753.93		$846.9651	$846.98	$846.95	$846.90