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	$132.56	8.447%	$143.7573	$143.76	$143.75	$143.80
Purchase #2	$195.72	6.725%	$208.8822	$208.88	$208.90	$208.90
Purchase #3	$115.40	13.380%	$130.8405	$130.84	$130.85	$130.80
Purchase #4	$57.31	4.437%	$59.8528	$59.85	$59.85	$59.90
Purchase #5	$107.83	8.315%	$116.7961	$116.80	$116.80	$116.80
Purchase #6	$89.95	5.464%	$94.8649	$94.86	$94.85	$94.90
Purchase #7	$127.94	12.727%	$144.2229	$144.22	$144.20	$144.20
7 purchase totals =	$826.71		$899.2167	$899.21	$899.20	$899.30