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	$72.49	7.223%	$77.726	$77.73	$77.75	$77.70
Purchase #2	$241.31	7.747%	$260.0043	$260.00	$260.00	$260.00
Purchase #3	$50.40	8.425%	$54.6462	$54.65	$54.65	$54.60
Purchase #4	$116.79	12.639%	$131.5511	$131.55	$131.55	$131.60
Purchase #5	$172.25	10.493%	$190.3242	$190.32	$190.30	$190.30
Purchase #6	$18.33	10.731%	$20.297	$20.30	$20.30	$20.30
Purchase #7	$144.59	5.175%	$152.0725	$152.07	$152.05	$152.10
7 purchase totals =	$816.16		$886.6213	$886.62	$886.60	$886.60