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	$170.96	13.165%	$193.4669	$193.47	$193.45	$193.50
Purchase #2	$135.84	11.549%	$151.5282	$151.53	$151.55	$151.50
Purchase #3	$53.35	7.330%	$57.2606	$57.26	$57.25	$57.30
Purchase #4	$173.60	8.776%	$188.8351	$188.84	$188.85	$188.80
Purchase #5	$238.49	5.142%	$250.7532	$250.75	$250.75	$250.80
Purchase #6	$16.81	4.686%	$17.5977	$17.60	$17.60	$17.60
Purchase #7	$145.52	7.783%	$156.8458	$156.85	$156.85	$156.80
7 purchase totals =	$934.57		$1,016.2875	$1,016.30	$1,016.30	$1,016.30