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	$91.30	9.721%	$100.1753	$100.18	$100.20	$100.20
Purchase #2	$146.92	3.727%	$152.3957	$152.40	$152.40	$152.40
Purchase #3	$172.85	7.566%	$185.9278	$185.93	$185.95	$185.90
Purchase #4	$104.27	5.435%	$109.9371	$109.94	$109.95	$109.90
Purchase #5	$222.54	12.733%	$250.876	$250.88	$250.90	$250.90
Purchase #6	$112.59	11.299%	$125.3115	$125.31	$125.30	$125.30
Purchase #7	$162.77	6.842%	$173.9067	$173.91	$173.90	$173.90
7 purchase totals =	$1,013.24		$1,098.5301	$1,098.55	$1,098.60	$1,098.50