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	$151.62	13.540%	$172.1493	$172.15	$172.15	$172.10
Purchase #2	$129.74	7.858%	$139.935	$139.94	$139.95	$139.90
Purchase #3	$187.68	13.633%	$213.2664	$213.27	$213.25	$213.30
Purchase #4	$91.89	9.236%	$100.377	$100.38	$100.40	$100.40
Purchase #5	$157.34	5.400%	$165.8364	$165.84	$165.85	$165.80
Purchase #6	$160.40	11.644%	$179.077	$179.08	$179.10	$179.10
Purchase #7	$154.81	3.145%	$159.6788	$159.68	$159.70	$159.70
7 purchase totals =	$1,033.48		$1,130.3199	$1,130.34	$1,130.40	$1,130.30