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	$213.97	11.406%	$238.3754	$238.38	$238.40	$238.40
Purchase #2	$144.60	12.325%	$162.422	$162.42	$162.40	$162.40
Purchase #3	$172.42	11.259%	$191.8328	$191.83	$191.85	$191.80
Purchase #4	$65.49	9.747%	$71.8733	$71.87	$71.85	$71.90
Purchase #5	$9.35	9.306%	$10.2201	$10.22	$10.20	$10.20
Purchase #6	$153.71	7.144%	$164.691	$164.69	$164.70	$164.70
Purchase #7	$146.91	4.553%	$153.5988	$153.60	$153.60	$153.60
7 purchase totals =	$906.45		$993.0134	$993.01	$993.00	$993.00