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	$61.47	6.440%	$65.4287	$65.43	$65.45	$65.40
Purchase #2	$52.37	12.210%	$58.7644	$58.76	$58.75	$58.80
Purchase #3	$44.59	12.644%	$50.228	$50.23	$50.25	$50.20
Purchase #4	$184.73	11.195%	$205.4105	$205.41	$205.40	$205.40
Purchase #5	$70.27	11.455%	$78.3194	$78.32	$78.30	$78.30
Purchase #6	$213.42	13.714%	$242.6884	$242.69	$242.70	$242.70
Purchase #7	$34.74	6.868%	$37.1259	$37.13	$37.15	$37.10
7 purchase totals =	$661.59		$737.9653	$737.97	$738.00	$737.90