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	$216.69	10.255%	$238.9116	$238.91	$238.90	$238.90
Purchase #2	$221.29	13.135%	$250.3564	$250.36	$250.35	$250.40
Purchase #3	$94.92	5.242%	$99.8957	$99.90	$99.90	$99.90
Purchase #4	$38.90	11.261%	$43.2805	$43.28	$43.30	$43.30
Purchase #5	$91.27	4.721%	$95.5789	$95.58	$95.60	$95.60
Purchase #6	$65.54	13.491%	$74.382	$74.38	$74.40	$74.40
Purchase #7	$131.87	11.206%	$146.6474	$146.65	$146.65	$146.60
7 purchase totals =	$860.48		$949.0525	$949.06	$949.10	$949.10