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	$130.60	11.323%	$145.3878	$145.39	$145.40	$145.40
Purchase #2	$146.51	4.529%	$153.1454	$153.15	$153.15	$153.10
Purchase #3	$118.84	11.691%	$132.7336	$132.73	$132.75	$132.70
Purchase #4	$37.57	13.137%	$42.5056	$42.51	$42.50	$42.50
Purchase #5	$177.48	10.653%	$196.3869	$196.39	$196.40	$196.40
Purchase #6	$85.72	6.404%	$91.2095	$91.21	$91.20	$91.20
Purchase #7	$110.91	8.657%	$120.5115	$120.51	$120.50	$120.50
7 purchase totals =	$807.63		$881.8803	$881.89	$881.90	$881.80