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	$154.70	12.422%	$173.9168	$173.92	$173.90	$173.90
Purchase #2	$10.42	4.224%	$10.8601	$10.86	$10.85	$10.90
Purchase #3	$127.63	10.597%	$141.155	$141.16	$141.15	$141.20
Purchase #4	$105.37	4.864%	$110.4952	$110.50	$110.50	$110.50
Purchase #5	$248.87	8.227%	$269.3445	$269.34	$269.35	$269.30
Purchase #6	$31.89	12.519%	$35.8823	$35.88	$35.90	$35.90
Purchase #7	$157.78	8.286%	$170.8537	$170.85	$170.85	$170.90
7 purchase totals =	$836.66		$912.5076	$912.51	$912.50	$912.60