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	$124.45	7.552%	$133.8485	$133.85	$133.85	$133.80
Purchase #2	$67.43	12.551%	$75.8931	$75.89	$75.90	$75.90
Purchase #3	$52.69	13.725%	$59.9217	$59.92	$59.90	$59.90
Purchase #4	$205.95	10.177%	$226.9095	$226.91	$226.90	$226.90
Purchase #5	$159.90	8.242%	$173.079	$173.08	$173.10	$173.10
Purchase #6	$175.44	11.833%	$196.1998	$196.20	$196.20	$196.20
Purchase #7	$34.41	3.506%	$35.6164	$35.62	$35.60	$35.60
7 purchase totals =	$820.27		$901.4680	$901.47	$901.45	$901.40