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	$247.38	11.368%	$275.5022	$275.50	$275.50	$275.50
Purchase #2	$6.85	9.105%	$7.4737	$7.47	$7.45	$7.50
Purchase #3	$214.61	12.158%	$240.7023	$240.70	$240.70	$240.70
Purchase #4	$76.53	11.688%	$85.4748	$85.47	$85.45	$85.50
Purchase #5	$34.86	13.493%	$39.5637	$39.56	$39.55	$39.60
Purchase #6	$72.25	4.316%	$75.3683	$75.37	$75.35	$75.40
Purchase #7	$184.54	6.207%	$195.9944	$195.99	$196.00	$196.00
7 purchase totals =	$837.02		$920.0794	$920.06	$920.00	$920.20