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	$174.76	12.671%	$196.9038	$196.90	$196.90	$196.90
Purchase #2	$21.61	5.220%	$22.738	$22.74	$22.75	$22.70
Purchase #3	$52.95	11.846%	$59.2225	$59.22	$59.20	$59.20
Purchase #4	$51.70	12.462%	$58.1429	$58.14	$58.15	$58.10
Purchase #5	$106.69	8.722%	$115.9955	$116.00	$116.00	$116.00
Purchase #6	$246.43	13.392%	$279.4319	$279.43	$279.45	$279.40
Purchase #7	$127.49	3.670%	$132.1689	$132.17	$132.15	$132.20
7 purchase totals =	$781.63		$864.6035	$864.60	$864.60	$864.50