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	$60.50	4.739%	$63.3671	$63.37	$63.35	$63.40
Purchase #2	$127.66	7.681%	$137.4656	$137.47	$137.45	$137.50
Purchase #3	$184.75	4.193%	$192.4966	$192.50	$192.50	$192.50
Purchase #4	$167.29	12.604%	$188.3752	$188.38	$188.40	$188.40
Purchase #5	$138.60	3.246%	$143.099	$143.10	$143.10	$143.10
Purchase #6	$240.38	3.338%	$248.4039	$248.40	$248.40	$248.40
Purchase #7	$101.27	11.825%	$113.2452	$113.25	$113.25	$113.20
7 purchase totals =	$1,020.45		$1,086.4526	$1,086.47	$1,086.45	$1,086.50