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	$113.32	8.766%	$123.2536	$123.25	$123.25	$123.30
Purchase #2	$104.39	5.130%	$109.7452	$109.75	$109.75	$109.70
Purchase #3	$94.43	9.229%	$103.1449	$103.14	$103.15	$103.10
Purchase #4	$204.58	6.288%	$217.444	$217.44	$217.45	$217.40
Purchase #5	$119.52	10.766%	$132.3875	$132.39	$132.40	$132.40
Purchase #6	$137.43	8.698%	$149.3837	$149.38	$149.40	$149.40
Purchase #7	$102.89	5.675%	$108.729	$108.73	$108.75	$108.70
7 purchase totals =	$876.56		$944.0879	$944.08	$944.15	$944.00