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	$192.84	6.614%	$205.5944	$205.59	$205.60	$205.60
Purchase #2	$172.89	6.172%	$183.5608	$183.56	$183.55	$183.60
Purchase #3	$100.69	7.558%	$108.3002	$108.30	$108.30	$108.30
Purchase #4	$20.28	5.803%	$21.4568	$21.46	$21.45	$21.50
Purchase #5	$133.42	9.514%	$146.1136	$146.11	$146.10	$146.10
Purchase #6	$142.78	4.743%	$149.5521	$149.55	$149.55	$149.60
Purchase #7	$74.30	4.303%	$77.4971	$77.50	$77.50	$77.50
7 purchase totals =	$837.20		$892.0750	$892.07	$892.05	$892.20