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	$129.82	3.600%	$134.4935	$134.49	$134.50	$134.50
Purchase #2	$24.81	13.277%	$28.104	$28.10	$28.10	$28.10
Purchase #3	$208.81	3.720%	$216.5777	$216.58	$216.60	$216.60
Purchase #4	$17.86	12.522%	$20.0964	$20.10	$20.10	$20.10
Purchase #5	$188.38	8.563%	$204.511	$204.51	$204.50	$204.50
Purchase #6	$80.25	6.484%	$85.4534	$85.45	$85.45	$85.50
Purchase #7	$214.41	3.217%	$221.3076	$221.31	$221.30	$221.30
7 purchase totals =	$864.34		$910.5436	$910.54	$910.55	$910.60