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	$161.92	6.326%	$172.1631	$172.16	$172.15	$172.20
Purchase #2	$131.96	10.124%	$145.3196	$145.32	$145.30	$145.30
Purchase #3	$214.80	13.260%	$243.2825	$243.28	$243.30	$243.30
Purchase #4	$34.63	11.417%	$38.5837	$38.58	$38.60	$38.60
Purchase #5	$158.40	4.602%	$165.6896	$165.69	$165.70	$165.70
Purchase #6	$196.31	13.568%	$222.9453	$222.95	$222.95	$222.90
Purchase #7	$175.60	11.828%	$196.37	$196.37	$196.35	$196.40
7 purchase totals =	$1,073.62		$1,184.3538	$1,184.35	$1,184.35	$1,184.40