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	$40.72	11.578%	$45.4346	$45.43	$45.45	$45.40
Purchase #2	$13.64	8.694%	$14.8259	$14.83	$14.85	$14.80
Purchase #3	$245.75	3.637%	$254.6879	$254.69	$254.70	$254.70
Purchase #4	$151.47	3.470%	$156.726	$156.73	$156.75	$156.70
Purchase #5	$238.49	10.115%	$262.6133	$262.61	$262.60	$262.60
Purchase #6	$154.81	7.259%	$166.0477	$166.05	$166.05	$166.00
Purchase #7	$35.42	13.505%	$40.2035	$40.20	$40.20	$40.20
7 purchase totals =	$880.30		$940.5389	$940.54	$940.60	$940.40