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	$27.95	5.286%	$29.4274	$29.43	$29.45	$29.40
Purchase #2	$35.41	13.456%	$40.1748	$40.17	$40.15	$40.20
Purchase #3	$202.93	9.487%	$222.182	$222.18	$222.20	$222.20
Purchase #4	$9.43	10.208%	$10.3926	$10.39	$10.40	$10.40
Purchase #5	$181.39	5.270%	$190.9493	$190.95	$190.95	$190.90
Purchase #6	$20.77	10.320%	$22.9135	$22.91	$22.90	$22.90
Purchase #7	$36.68	11.609%	$40.9382	$40.94	$40.95	$40.90
7 purchase totals =	$514.56		$556.9778	$556.97	$557.00	$556.90