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	$192.74	8.169%	$208.4849	$208.48	$208.50	$208.50
Purchase #2	$98.67	12.659%	$111.1606	$111.16	$111.15	$111.20
Purchase #3	$143.29	11.865%	$160.2914	$160.29	$160.30	$160.30
Purchase #4	$67.40	9.823%	$74.0207	$74.02	$74.00	$74.00
Purchase #5	$176.96	13.463%	$200.7841	$200.78	$200.80	$200.80
Purchase #6	$156.91	8.234%	$169.83	$169.83	$169.85	$169.80
Purchase #7	$237.26	4.426%	$247.7611	$247.76	$247.75	$247.80
7 purchase totals =	$1,073.23		$1,172.3328	$1,172.32	$1,172.35	$1,172.40