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	$67.78	11.554%	$75.6113	$75.61	$75.60	$75.60
Purchase #2	$228.96	9.536%	$250.7936	$250.79	$250.80	$250.80
Purchase #3	$66.73	7.528%	$71.7534	$71.75	$71.75	$71.80
Purchase #4	$243.38	11.262%	$270.7895	$270.79	$270.80	$270.80
Purchase #5	$119.82	6.162%	$127.2033	$127.20	$127.20	$127.20
Purchase #6	$15.42	3.145%	$15.905	$15.91	$15.90	$15.90
Purchase #7	$232.98	7.189%	$249.7289	$249.73	$249.75	$249.70
7 purchase totals =	$975.07		$1,061.7850	$1,061.78	$1,061.80	$1,061.80