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	$181.43	5.619%	$191.6246	$191.62	$191.60	$191.60
Purchase #2	$9.31	12.439%	$10.4681	$10.47	$10.45	$10.50
Purchase #3	$145.30	4.563%	$151.93	$151.93	$151.95	$151.90
Purchase #4	$53.89	13.513%	$61.1722	$61.17	$61.15	$61.20
Purchase #5	$66.57	8.493%	$72.2238	$72.22	$72.20	$72.20
Purchase #6	$36.53	12.578%	$41.1247	$41.12	$41.10	$41.10
Purchase #7	$227.81	4.555%	$238.1867	$238.19	$238.20	$238.20
7 purchase totals =	$720.84		$766.7301	$766.72	$766.65	$766.70