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	$146.74	9.619%	$160.8549	$160.85	$160.85	$160.90
Purchase #2	$66.29	8.841%	$72.1507	$72.15	$72.15	$72.20
Purchase #3	$50.31	6.424%	$53.5419	$53.54	$53.55	$53.50
Purchase #4	$34.31	6.629%	$36.5844	$36.58	$36.60	$36.60
Purchase #5	$89.95	10.660%	$99.5387	$99.54	$99.55	$99.50
Purchase #6	$41.96	7.830%	$45.2455	$45.25	$45.25	$45.20
Purchase #7	$216.84	6.410%	$230.7394	$230.74	$230.75	$230.70
7 purchase totals =	$646.40		$698.6555	$698.65	$698.70	$698.60