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	$117.69	8.165%	$127.2994	$127.30	$127.30	$127.30
Purchase #2	$109.50	6.384%	$116.4905	$116.49	$116.50	$116.50
Purchase #3	$225.40	5.548%	$237.9052	$237.91	$237.90	$237.90
Purchase #4	$105.36	12.798%	$118.844	$118.84	$118.85	$118.80
Purchase #5	$89.36	7.337%	$95.9163	$95.92	$95.90	$95.90
Purchase #6	$242.32	10.395%	$267.5092	$267.51	$267.50	$267.50
Purchase #7	$242.62	6.853%	$259.2467	$259.25	$259.25	$259.20
7 purchase totals =	$1,132.25		$1,223.2113	$1,223.22	$1,223.20	$1,223.10