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	$38.80	13.800%	$44.1544	$44.15	$44.15	$44.20
Purchase #2	$141.85	9.493%	$155.3158	$155.32	$155.30	$155.30
Purchase #3	$158.25	4.830%	$165.8935	$165.89	$165.90	$165.90
Purchase #4	$70.47	6.112%	$74.7771	$74.78	$74.80	$74.80
Purchase #5	$165.29	4.238%	$172.295	$172.30	$172.30	$172.30
Purchase #6	$181.78	13.568%	$206.4439	$206.44	$206.45	$206.40
Purchase #7	$206.39	6.450%	$219.7022	$219.70	$219.70	$219.70
7 purchase totals =	$962.83		$1,038.5819	$1,038.58	$1,038.60	$1,038.60