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	$220.65	3.851%	$229.1472	$229.15	$229.15	$229.10
Purchase #2	$132.28	11.754%	$147.8282	$147.83	$147.85	$147.80
Purchase #3	$91.37	8.774%	$99.3868	$99.39	$99.40	$99.40
Purchase #4	$136.95	10.368%	$151.149	$151.15	$151.15	$151.10
Purchase #5	$230.98	10.219%	$254.5838	$254.58	$254.60	$254.60
Purchase #6	$127.95	4.610%	$133.8485	$133.85	$133.85	$133.80
Purchase #7	$44.38	3.719%	$46.0305	$46.03	$46.05	$46.00
7 purchase totals =	$984.56		$1,061.9740	$1,061.98	$1,062.05	$1,061.80