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	$159.58	10.724%	$176.6934	$176.69	$176.70	$176.70
Purchase #2	$29.33	11.739%	$32.773	$32.77	$32.75	$32.80
Purchase #3	$18.47	9.651%	$20.2525	$20.25	$20.25	$20.30
Purchase #4	$55.65	8.394%	$60.3213	$60.32	$60.30	$60.30
Purchase #5	$133.70	12.377%	$150.248	$150.25	$150.25	$150.20
Purchase #6	$101.26	11.109%	$112.509	$112.51	$112.50	$112.50
Purchase #7	$167.64	8.321%	$181.5893	$181.59	$181.60	$181.60
7 purchase totals =	$665.63		$734.3865	$734.38	$734.35	$734.40