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	$108.79	9.785%	$119.4351	$119.44	$119.45	$119.40
Purchase #2	$218.42	11.823%	$244.2438	$244.24	$244.25	$244.20
Purchase #3	$32.40	7.731%	$34.9048	$34.90	$34.90	$34.90
Purchase #4	$11.77	9.391%	$12.8753	$12.88	$12.90	$12.90
Purchase #5	$113.98	12.202%	$127.8878	$127.89	$127.90	$127.90
Purchase #6	$187.28	6.474%	$199.4045	$199.40	$199.40	$199.40
Purchase #7	$46.60	12.604%	$52.4735	$52.47	$52.45	$52.50
7 purchase totals =	$719.24		$791.2248	$791.22	$791.25	$791.20