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	$119.58	12.540%	$134.5753	$134.58	$134.60	$134.60
Purchase #2	$148.39	11.615%	$165.6255	$165.63	$165.65	$165.60
Purchase #3	$161.47	5.426%	$170.2314	$170.23	$170.25	$170.20
Purchase #4	$43.51	10.674%	$48.1543	$48.15	$48.15	$48.20
Purchase #5	$72.88	7.780%	$78.5501	$78.55	$78.55	$78.60
Purchase #6	$146.74	9.602%	$160.83	$160.83	$160.85	$160.80
Purchase #7	$41.68	5.761%	$44.0812	$44.08	$44.10	$44.10
7 purchase totals =	$734.25		$802.0478	$802.05	$802.15	$802.10