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	$103.71	7.277%	$111.257	$111.26	$111.25	$111.30
Purchase #2	$132.96	10.359%	$146.7333	$146.73	$146.75	$146.70
Purchase #3	$146.41	3.761%	$151.9165	$151.92	$151.90	$151.90
Purchase #4	$92.32	4.252%	$96.2454	$96.25	$96.25	$96.20
Purchase #5	$161.57	7.247%	$173.279	$173.28	$173.30	$173.30
Purchase #6	$166.51	4.193%	$173.4918	$173.49	$173.50	$173.50
Purchase #7	$173.57	4.245%	$180.938	$180.94	$180.95	$180.90
7 purchase totals =	$977.05		$1,033.8610	$1,033.87	$1,033.90	$1,033.80