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	$36.61	8.307%	$39.6512	$39.65	$39.65	$39.70
Purchase #2	$74.90	7.624%	$80.6104	$80.61	$80.60	$80.60
Purchase #3	$104.65	6.502%	$111.4543	$111.45	$111.45	$111.50
Purchase #4	$107.28	6.174%	$113.9035	$113.90	$113.90	$113.90
Purchase #5	$236.32	9.224%	$258.1182	$258.12	$258.10	$258.10
Purchase #6	$45.26	11.555%	$50.4898	$50.49	$50.50	$50.50
Purchase #7	$89.94	9.142%	$98.1623	$98.16	$98.15	$98.20
7 purchase totals =	$694.96		$752.3897	$752.38	$752.35	$752.50