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	$63.93	3.622%	$66.2455	$66.25	$66.25	$66.20
Purchase #2	$172.77	7.296%	$185.3753	$185.38	$185.40	$185.40
Purchase #3	$187.32	11.117%	$208.1444	$208.14	$208.15	$208.10
Purchase #4	$57.91	6.789%	$61.8415	$61.84	$61.85	$61.80
Purchase #5	$53.31	8.143%	$57.651	$57.65	$57.65	$57.70
Purchase #6	$229.56	6.675%	$244.8831	$244.88	$244.90	$244.90
Purchase #7	$108.98	9.617%	$119.4606	$119.46	$119.45	$119.50
7 purchase totals =	$873.78		$943.6014	$943.60	$943.65	$943.60