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	$229.73	11.269%	$255.6183	$255.62	$255.60	$255.60
Purchase #2	$241.38	12.843%	$272.3804	$272.38	$272.40	$272.40
Purchase #3	$157.27	6.185%	$166.9971	$167.00	$167.00	$167.00
Purchase #4	$164.46	5.178%	$172.9757	$172.98	$173.00	$173.00
Purchase #5	$141.79	3.543%	$146.8136	$146.81	$146.80	$146.80
Purchase #6	$165.31	8.463%	$179.3002	$179.30	$179.30	$179.30
Purchase #7	$26.67	7.470%	$28.6622	$28.66	$28.65	$28.70
7 purchase totals =	$1,126.61		$1,222.7475	$1,222.75	$1,222.75	$1,222.80