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	$22.48	11.452%	$25.0544	$25.05	$25.05	$25.10
Purchase #2	$128.67	10.830%	$142.605	$142.61	$142.60	$142.60
Purchase #3	$141.49	9.701%	$155.2159	$155.22	$155.20	$155.20
Purchase #4	$242.28	13.563%	$275.1404	$275.14	$275.15	$275.10
Purchase #5	$163.99	4.722%	$171.7336	$171.73	$171.75	$171.70
Purchase #6	$152.71	13.578%	$173.445	$173.45	$173.45	$173.40
Purchase #7	$179.58	11.520%	$200.2676	$200.27	$200.25	$200.30
7 purchase totals =	$1,031.20		$1,143.4619	$1,143.47	$1,143.45	$1,143.40