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	$101.59	10.194%	$111.9461	$111.95	$111.95	$111.90
Purchase #2	$126.31	5.181%	$132.8541	$132.85	$132.85	$132.90
Purchase #3	$186.79	6.598%	$199.1144	$199.11	$199.10	$199.10
Purchase #4	$34.75	10.526%	$38.4078	$38.41	$38.40	$38.40
Purchase #5	$28.88	12.816%	$32.5813	$32.58	$32.60	$32.60
Purchase #6	$80.37	7.105%	$86.0803	$86.08	$86.10	$86.10
Purchase #7	$234.58	8.633%	$254.8313	$254.83	$254.85	$254.80
7 purchase totals =	$793.27		$855.8153	$855.81	$855.85	$855.80