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	$207.55	13.194%	$234.9341	$234.93	$234.95	$234.90
Purchase #2	$102.71	8.733%	$111.6797	$111.68	$111.70	$111.70
Purchase #3	$52.46	8.322%	$56.8257	$56.83	$56.85	$56.80
Purchase #4	$73.86	6.374%	$78.5678	$78.57	$78.55	$78.60
Purchase #5	$13.56	9.717%	$14.8776	$14.88	$14.90	$14.90
Purchase #6	$194.49	11.584%	$217.0197	$217.02	$217.00	$217.00
Purchase #7	$202.26	6.572%	$215.5525	$215.55	$215.55	$215.60
7 purchase totals =	$846.89		$929.4571	$929.46	$929.50	$929.50