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	$42.78	13.716%	$48.6477	$48.65	$48.65	$48.60
Purchase #2	$111.27	9.845%	$122.2245	$122.22	$122.20	$122.20
Purchase #3	$88.37	9.702%	$96.9437	$96.94	$96.95	$96.90
Purchase #4	$242.51	5.809%	$256.5974	$256.60	$256.60	$256.60
Purchase #5	$39.40	5.607%	$41.6092	$41.61	$41.60	$41.60
Purchase #6	$158.75	3.797%	$164.7777	$164.78	$164.80	$164.80
Purchase #7	$213.36	4.856%	$223.7208	$223.72	$223.70	$223.70
7 purchase totals =	$896.44		$954.5210	$954.52	$954.50	$954.40