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	$66.93	8.867%	$72.8647	$72.86	$72.85	$72.90
Purchase #2	$95.37	13.552%	$108.2945	$108.29	$108.30	$108.30
Purchase #3	$36.60	10.529%	$40.4536	$40.45	$40.45	$40.50
Purchase #4	$10.33	7.780%	$11.1337	$11.13	$11.15	$11.10
Purchase #5	$106.75	11.418%	$118.9387	$118.94	$118.95	$118.90
Purchase #6	$97.92	11.840%	$109.5137	$109.51	$109.50	$109.50
Purchase #7	$10.72	13.207%	$12.1358	$12.14	$12.15	$12.10
7 purchase totals =	$424.62		$473.3347	$473.32	$473.35	$473.30