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	$169.81	8.625%	$184.4561	$184.46	$184.45	$184.50
Purchase #2	$48.71	4.850%	$51.0724	$51.07	$51.05	$51.10
Purchase #3	$234.68	11.650%	$262.0202	$262.02	$262.00	$262.00
Purchase #4	$68.65	5.727%	$72.5816	$72.58	$72.60	$72.60
Purchase #5	$136.53	4.220%	$142.2916	$142.29	$142.30	$142.30
Purchase #6	$35.81	11.487%	$39.9235	$39.92	$39.90	$39.90
Purchase #7	$116.89	13.391%	$132.5427	$132.54	$132.55	$132.50
7 purchase totals =	$811.08		$884.8881	$884.88	$884.85	$884.90