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	$190.88	9.479%	$208.9735	$208.97	$208.95	$209.00
Purchase #2	$100.94	4.653%	$105.6367	$105.64	$105.65	$105.60
Purchase #3	$138.81	10.336%	$153.1574	$153.16	$153.15	$153.20
Purchase #4	$231.58	3.501%	$239.6876	$239.69	$239.70	$239.70
Purchase #5	$31.28	13.563%	$35.5225	$35.52	$35.50	$35.50
Purchase #6	$85.82	5.671%	$90.6869	$90.69	$90.70	$90.70
Purchase #7	$131.58	5.817%	$139.234	$139.23	$139.25	$139.20
7 purchase totals =	$910.89		$972.8986	$972.90	$972.90	$972.90