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	$42.38	10.237%	$46.7184	$46.72	$46.70	$46.70
Purchase #2	$30.62	10.558%	$33.8529	$33.85	$33.85	$33.90
Purchase #3	$133.31	13.455%	$151.2469	$151.25	$151.25	$151.20
Purchase #4	$89.43	13.325%	$101.3465	$101.35	$101.35	$101.30
Purchase #5	$211.49	4.237%	$220.4508	$220.45	$220.45	$220.50
Purchase #6	$10.28	4.756%	$10.7689	$10.77	$10.75	$10.80
Purchase #7	$137.65	9.670%	$150.9608	$150.96	$150.95	$151.00
7 purchase totals =	$655.16		$715.3452	$715.35	$715.30	$715.40