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	$122.31	5.399%	$128.9135	$128.91	$128.90	$128.90
Purchase #2	$78.69	5.289%	$82.8519	$82.85	$82.85	$82.90
Purchase #3	$214.60	5.380%	$226.1455	$226.15	$226.15	$226.10
Purchase #4	$12.33	12.392%	$13.8579	$13.86	$13.85	$13.90
Purchase #5	$46.96	3.536%	$48.6205	$48.62	$48.60	$48.60
Purchase #6	$187.65	11.169%	$208.6086	$208.61	$208.60	$208.60
Purchase #7	$209.92	11.733%	$234.5499	$234.55	$234.55	$234.50
7 purchase totals =	$872.46		$943.5478	$943.55	$943.50	$943.50