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	$233.53	3.409%	$241.491	$241.49	$241.50	$241.50
Purchase #2	$113.39	12.792%	$127.8948	$127.89	$127.90	$127.90
Purchase #3	$90.98	6.720%	$97.0939	$97.09	$97.10	$97.10
Purchase #4	$13.89	12.817%	$15.6703	$15.67	$15.65	$15.70
Purchase #5	$56.55	10.359%	$62.408	$62.41	$62.40	$62.40
Purchase #6	$24.70	10.733%	$27.3511	$27.35	$27.35	$27.40
Purchase #7	$169.30	4.485%	$176.8931	$176.89	$176.90	$176.90
7 purchase totals =	$702.34		$748.8022	$748.79	$748.80	$748.90