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	$69.46	12.412%	$78.0814	$78.08	$78.10	$78.10
Purchase #2	$97.43	3.563%	$100.9014	$100.90	$100.90	$100.90
Purchase #3	$133.84	13.781%	$152.2845	$152.28	$152.30	$152.30
Purchase #4	$34.65	4.347%	$36.1562	$36.16	$36.15	$36.20
Purchase #5	$37.69	3.672%	$39.074	$39.07	$39.05	$39.10
Purchase #6	$133.74	9.763%	$146.797	$146.80	$146.80	$146.80
Purchase #7	$183.61	4.180%	$191.2849	$191.28	$191.30	$191.30
7 purchase totals =	$690.42		$744.5794	$744.57	$744.60	$744.70