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	$175.42	9.364%	$191.8463	$191.85	$191.85	$191.80
Purchase #2	$39.89	13.626%	$45.3254	$45.33	$45.35	$45.30
Purchase #3	$100.44	4.829%	$105.2902	$105.29	$105.30	$105.30
Purchase #4	$67.29	5.386%	$70.9142	$70.91	$70.90	$70.90
Purchase #5	$143.51	4.141%	$149.4527	$149.45	$149.45	$149.50
Purchase #6	$101.66	6.819%	$108.5922	$108.59	$108.60	$108.60
Purchase #7	$6.92	3.194%	$7.141	$7.14	$7.15	$7.10
7 purchase totals =	$635.13		$678.5620	$678.56	$678.60	$678.50