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	$78.64	6.333%	$83.6203	$83.62	$83.60	$83.60
Purchase #2	$36.92	4.125%	$38.443	$38.44	$38.45	$38.40
Purchase #3	$121.98	9.513%	$133.584	$133.58	$133.60	$133.60
Purchase #4	$27.71	13.644%	$31.4908	$31.49	$31.50	$31.50
Purchase #5	$95.35	5.173%	$100.2825	$100.28	$100.30	$100.30
Purchase #6	$173.99	6.151%	$184.6921	$184.69	$184.70	$184.70
Purchase #7	$165.59	4.733%	$173.4274	$173.43	$173.45	$173.40
7 purchase totals =	$700.18		$745.5401	$745.53	$745.60	$745.50