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	$54.91	12.848%	$61.9648	$61.96	$61.95	$62.00
Purchase #2	$237.62	7.389%	$255.1777	$255.18	$255.20	$255.20
Purchase #3	$65.94	5.792%	$69.7592	$69.76	$69.75	$69.80
Purchase #4	$176.43	11.184%	$196.1619	$196.16	$196.15	$196.20
Purchase #5	$199.72	9.136%	$217.9664	$217.97	$217.95	$218.00
Purchase #6	$205.63	11.787%	$229.8676	$229.87	$229.85	$229.90
Purchase #7	$222.65	4.773%	$233.2771	$233.28	$233.30	$233.30
7 purchase totals =	$1,162.90		$1,264.1747	$1,264.18	$1,264.15	$1,264.40