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	$45.89	5.353%	$48.3465	$48.35	$48.35	$48.30
Purchase #2	$20.55	6.154%	$21.8146	$21.81	$21.80	$21.80
Purchase #3	$37.74	13.857%	$42.9696	$42.97	$42.95	$43.00
Purchase #4	$120.89	4.255%	$126.0339	$126.03	$126.05	$126.00
Purchase #5	$139.81	12.771%	$157.6651	$157.67	$157.65	$157.70
Purchase #6	$37.40	7.720%	$40.2873	$40.29	$40.30	$40.30
Purchase #7	$76.64	11.332%	$85.3248	$85.32	$85.30	$85.30
7 purchase totals =	$478.92		$522.4418	$522.44	$522.40	$522.40