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	$147.48	9.709%	$161.7988	$161.80	$161.80	$161.80
Purchase #2	$100.85	4.485%	$105.3731	$105.37	$105.35	$105.40
Purchase #3	$52.60	13.594%	$59.7504	$59.75	$59.75	$59.80
Purchase #4	$47.94	6.689%	$51.1467	$51.15	$51.15	$51.10
Purchase #5	$87.53	6.284%	$93.0304	$93.03	$93.05	$93.00
Purchase #6	$160.84	7.397%	$172.7373	$172.74	$172.75	$172.70
Purchase #7	$78.37	5.139%	$82.3974	$82.40	$82.40	$82.40
7 purchase totals =	$675.61		$726.2341	$726.24	$726.25	$726.20