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	$97.42	3.631%	$100.9573	$100.96	$100.95	$101.00
Purchase #2	$146.31	5.155%	$153.8523	$153.85	$153.85	$153.90
Purchase #3	$152.68	3.813%	$158.5017	$158.50	$158.50	$158.50
Purchase #4	$140.43	7.389%	$150.8064	$150.81	$150.80	$150.80
Purchase #5	$120.75	4.401%	$126.0642	$126.06	$126.05	$126.10
Purchase #6	$141.69	13.345%	$160.5985	$160.60	$160.60	$160.60
Purchase #7	$54.78	6.306%	$58.2344	$58.23	$58.25	$58.20
7 purchase totals =	$854.06		$909.0148	$909.01	$909.00	$909.10