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	$182.41	12.850%	$205.8497	$205.85	$205.85	$205.80
Purchase #2	$22.79	12.650%	$25.6729	$25.67	$25.65	$25.70
Purchase #3	$30.53	6.789%	$32.6027	$32.60	$32.60	$32.60
Purchase #4	$52.80	13.395%	$59.8726	$59.87	$59.85	$59.90
Purchase #5	$43.51	11.622%	$48.5667	$48.57	$48.55	$48.60
Purchase #6	$218.94	11.572%	$244.2757	$244.28	$244.30	$244.30
Purchase #7	$206.47	11.447%	$230.1046	$230.10	$230.10	$230.10
7 purchase totals =	$757.45		$846.9449	$846.94	$846.90	$847.00