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	$133.77	9.166%	$146.0314	$146.03	$146.05	$146.00
Purchase #2	$138.40	3.123%	$142.7222	$142.72	$142.70	$142.70
Purchase #3	$155.61	4.393%	$162.4459	$162.45	$162.45	$162.40
Purchase #4	$196.39	4.449%	$205.1274	$205.13	$205.15	$205.10
Purchase #5	$37.86	6.427%	$40.2933	$40.29	$40.30	$40.30
Purchase #6	$108.95	5.163%	$114.5751	$114.58	$114.60	$114.60
Purchase #7	$241.49	8.173%	$261.227	$261.23	$261.25	$261.20
7 purchase totals =	$1,012.47		$1,072.4223	$1,072.43	$1,072.50	$1,072.30