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	$227.88	8.466%	$247.1723	$247.17	$247.15	$247.20
Purchase #2	$189.71	8.389%	$205.6248	$205.62	$205.60	$205.60
Purchase #3	$142.76	5.418%	$150.4947	$150.49	$150.50	$150.50
Purchase #4	$142.89	7.431%	$153.5082	$153.51	$153.50	$153.50
Purchase #5	$80.88	5.391%	$85.2402	$85.24	$85.25	$85.20
Purchase #6	$145.38	11.612%	$162.2615	$162.26	$162.25	$162.30
Purchase #7	$66.44	5.649%	$70.1932	$70.19	$70.20	$70.20
7 purchase totals =	$995.94		$1,074.4949	$1,074.48	$1,074.45	$1,074.50