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	$229.43	4.614%	$240.0159	$240.02	$240.00	$240.00
Purchase #2	$165.95	4.671%	$173.7015	$173.70	$173.70	$173.70
Purchase #3	$225.26	13.619%	$255.9382	$255.94	$255.95	$255.90
Purchase #4	$173.79	10.390%	$191.8468	$191.85	$191.85	$191.80
Purchase #5	$23.60	11.246%	$26.2541	$26.25	$26.25	$26.30
Purchase #6	$89.71	5.456%	$94.6046	$94.60	$94.60	$94.60
Purchase #7	$157.55	4.611%	$164.8146	$164.81	$164.80	$164.80
7 purchase totals =	$1,065.29		$1,147.1757	$1,147.17	$1,147.15	$1,147.10