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	$145.95	4.246%	$152.147	$152.15	$152.15	$152.10
Purchase #2	$163.48	6.270%	$173.7302	$173.73	$173.75	$173.70
Purchase #3	$222.83	8.520%	$241.8151	$241.82	$241.80	$241.80
Purchase #4	$16.28	13.274%	$18.441	$18.44	$18.45	$18.40
Purchase #5	$19.29	3.806%	$20.0242	$20.02	$20.00	$20.00
Purchase #6	$18.91	8.207%	$20.4619	$20.46	$20.45	$20.50
Purchase #7	$153.71	13.304%	$174.1596	$174.16	$174.15	$174.20
7 purchase totals =	$740.45		$800.7790	$800.78	$800.75	$800.70