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	$33.38	3.490%	$34.545	$34.55	$34.55	$34.50
Purchase #2	$131.34	12.105%	$147.2387	$147.24	$147.25	$147.20
Purchase #3	$11.67	6.793%	$12.4627	$12.46	$12.45	$12.50
Purchase #4	$118.43	7.730%	$127.5846	$127.58	$127.60	$127.60
Purchase #5	$5.46	6.808%	$5.8317	$5.83	$5.85	$5.80
Purchase #6	$204.46	5.695%	$216.104	$216.10	$216.10	$216.10
Purchase #7	$142.89	10.869%	$158.4207	$158.42	$158.40	$158.40
7 purchase totals =	$647.63		$702.1874	$702.18	$702.20	$702.10