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	$155.93	11.260%	$173.4877	$173.49	$173.50	$173.50
Purchase #2	$146.96	6.324%	$156.2538	$156.25	$156.25	$156.30
Purchase #3	$169.34	8.795%	$184.2335	$184.23	$184.25	$184.20
Purchase #4	$33.48	11.224%	$37.2378	$37.24	$37.25	$37.20
Purchase #5	$183.30	12.256%	$205.7652	$205.77	$205.75	$205.80
Purchase #6	$105.37	5.475%	$111.139	$111.14	$111.15	$111.10
Purchase #7	$203.50	4.721%	$213.1072	$213.11	$213.10	$213.10
7 purchase totals =	$997.88		$1,081.2242	$1,081.23	$1,081.25	$1,081.20