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	$201.88	7.114%	$216.2417	$216.24	$216.25	$216.20
Purchase #2	$146.39	3.567%	$151.6117	$151.61	$151.60	$151.60
Purchase #3	$119.60	5.574%	$126.2665	$126.27	$126.25	$126.30
Purchase #4	$169.42	9.434%	$185.4031	$185.40	$185.40	$185.40
Purchase #5	$42.77	8.397%	$46.3614	$46.36	$46.35	$46.40
Purchase #6	$65.63	10.350%	$72.4227	$72.42	$72.40	$72.40
Purchase #7	$145.52	12.705%	$164.0083	$164.01	$164.00	$164.00
7 purchase totals =	$891.21		$962.3154	$962.31	$962.25	$962.30