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	$188.92	12.499%	$212.5331	$212.53	$212.55	$212.50
Purchase #2	$12.35	12.551%	$13.9	$13.90	$13.90	$13.90
Purchase #3	$167.32	10.215%	$184.4117	$184.41	$184.40	$184.40
Purchase #4	$118.64	7.492%	$127.5285	$127.53	$127.55	$127.50
Purchase #5	$203.54	5.491%	$214.7164	$214.72	$214.70	$214.70
Purchase #6	$93.44	11.339%	$104.0352	$104.04	$104.05	$104.00
Purchase #7	$91.81	8.197%	$99.3357	$99.34	$99.35	$99.30
7 purchase totals =	$876.02		$956.4606	$956.47	$956.50	$956.30