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	$229.82	10.778%	$254.59	$254.59	$254.60	$254.60
Purchase #2	$49.80	4.606%	$52.0938	$52.09	$52.10	$52.10
Purchase #3	$231.53	4.439%	$241.8076	$241.81	$241.80	$241.80
Purchase #4	$38.61	12.614%	$43.4803	$43.48	$43.50	$43.50
Purchase #5	$20.77	4.483%	$21.7011	$21.70	$21.70	$21.70
Purchase #6	$88.84	13.261%	$100.6211	$100.62	$100.60	$100.60
Purchase #7	$162.64	4.602%	$170.1247	$170.12	$170.10	$170.10
7 purchase totals =	$822.01		$884.4186	$884.41	$884.40	$884.40