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	$196.45	10.774%	$217.6155	$217.62	$217.60	$217.60
Purchase #2	$123.70	3.823%	$128.4291	$128.43	$128.45	$128.40
Purchase #3	$69.77	10.717%	$77.2473	$77.25	$77.25	$77.20
Purchase #4	$99.34	4.194%	$103.5063	$103.51	$103.50	$103.50
Purchase #5	$144.82	12.123%	$162.3765	$162.38	$162.40	$162.40
Purchase #6	$155.63	10.666%	$172.2295	$172.23	$172.25	$172.20
Purchase #7	$41.88	5.433%	$44.1553	$44.16	$44.15	$44.20
7 purchase totals =	$831.59		$905.5595	$905.58	$905.60	$905.50