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	$213.39	13.209%	$241.5767	$241.58	$241.60	$241.60
Purchase #2	$228.75	4.616%	$239.3091	$239.31	$239.30	$239.30
Purchase #3	$129.34	9.696%	$141.8808	$141.88	$141.90	$141.90
Purchase #4	$61.85	4.643%	$64.7217	$64.72	$64.70	$64.70
Purchase #5	$204.53	8.772%	$222.4714	$222.47	$222.45	$222.50
Purchase #6	$64.42	5.126%	$67.7222	$67.72	$67.70	$67.70
Purchase #7	$50.88	8.240%	$55.0725	$55.07	$55.05	$55.10
7 purchase totals =	$953.16		$1,032.7544	$1,032.75	$1,032.70	$1,032.80