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	$42.98	6.611%	$45.8214	$45.82	$45.80	$45.80
Purchase #2	$225.78	13.162%	$255.4972	$255.50	$255.50	$255.50
Purchase #3	$111.75	11.415%	$124.5063	$124.51	$124.50	$124.50
Purchase #4	$31.57	8.586%	$34.2806	$34.28	$34.30	$34.30
Purchase #5	$223.74	5.201%	$235.3767	$235.38	$235.40	$235.40
Purchase #6	$238.67	8.614%	$259.229	$259.23	$259.25	$259.20
Purchase #7	$100.41	8.234%	$108.6778	$108.68	$108.70	$108.70
7 purchase totals =	$974.90		$1,063.3890	$1,063.40	$1,063.45	$1,063.40