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	$147.77	3.239%	$152.5563	$152.56	$152.55	$152.60
Purchase #2	$50.97	13.707%	$57.9565	$57.96	$57.95	$58.00
Purchase #3	$131.25	10.185%	$144.6178	$144.62	$144.60	$144.60
Purchase #4	$75.45	10.607%	$83.453	$83.45	$83.45	$83.50
Purchase #5	$236.40	9.821%	$259.6168	$259.62	$259.60	$259.60
Purchase #6	$145.42	5.106%	$152.8451	$152.85	$152.85	$152.80
Purchase #7	$229.70	7.201%	$246.2407	$246.24	$246.25	$246.20
7 purchase totals =	$1,016.96		$1,097.2862	$1,097.30	$1,097.25	$1,097.30