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	$43.38	6.274%	$46.1017	$46.10	$46.10	$46.10
Purchase #2	$27.60	8.303%	$29.8916	$29.89	$29.90	$29.90
Purchase #3	$215.83	10.545%	$238.5893	$238.59	$238.60	$238.60
Purchase #4	$78.36	4.222%	$81.6684	$81.67	$81.65	$81.70
Purchase #5	$158.43	4.693%	$165.8651	$165.87	$165.85	$165.90
Purchase #6	$61.98	13.210%	$70.1676	$70.17	$70.15	$70.20
Purchase #7	$165.94	11.137%	$184.4207	$184.42	$184.40	$184.40
7 purchase totals =	$751.52		$816.7044	$816.71	$816.65	$816.80