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	$204.95	13.861%	$233.3581	$233.36	$233.35	$233.40
Purchase #2	$192.70	10.541%	$213.0125	$213.01	$213.00	$213.00
Purchase #3	$165.27	4.428%	$172.5882	$172.59	$172.60	$172.60
Purchase #4	$211.25	8.733%	$229.6985	$229.70	$229.70	$229.70
Purchase #5	$34.82	7.318%	$37.3681	$37.37	$37.35	$37.40
Purchase #6	$160.32	7.383%	$172.1564	$172.16	$172.15	$172.20
Purchase #7	$205.73	3.598%	$213.1322	$213.13	$213.15	$213.10
7 purchase totals =	$1,175.04		$1,271.3140	$1,271.32	$1,271.30	$1,271.40