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	$117.61	13.773%	$133.8084	$133.81	$133.80	$133.80
Purchase #2	$73.52	6.697%	$78.4436	$78.44	$78.45	$78.40
Purchase #3	$130.54	11.173%	$145.1252	$145.13	$145.15	$145.10
Purchase #4	$24.29	10.310%	$26.7943	$26.79	$26.80	$26.80
Purchase #5	$17.41	4.766%	$18.2398	$18.24	$18.25	$18.20
Purchase #6	$103.63	12.532%	$116.6169	$116.62	$116.60	$116.60
Purchase #7	$31.77	5.708%	$33.5834	$33.58	$33.60	$33.60
7 purchase totals =	$498.77		$552.6116	$552.61	$552.65	$552.50