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	$194.45	8.105%	$210.2102	$210.21	$210.20	$210.20
Purchase #2	$96.81	4.440%	$101.1084	$101.11	$101.10	$101.10
Purchase #3	$100.87	3.833%	$104.7363	$104.74	$104.75	$104.70
Purchase #4	$151.64	9.849%	$166.575	$166.58	$166.60	$166.60
Purchase #5	$199.29	12.114%	$223.432	$223.43	$223.45	$223.40
Purchase #6	$216.86	11.211%	$241.1722	$241.17	$241.15	$241.20
Purchase #7	$81.52	13.250%	$92.3214	$92.32	$92.30	$92.30
7 purchase totals =	$1,041.44		$1,139.5555	$1,139.56	$1,139.55	$1,139.50