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	$221.36	10.304%	$244.1689	$244.17	$244.15	$244.20
Purchase #2	$27.48	10.719%	$30.4256	$30.43	$30.45	$30.40
Purchase #3	$63.85	13.225%	$72.2942	$72.29	$72.30	$72.30
Purchase #4	$191.78	10.484%	$211.8862	$211.89	$211.90	$211.90
Purchase #5	$18.52	10.664%	$20.495	$20.50	$20.50	$20.50
Purchase #6	$60.77	9.292%	$66.4167	$66.42	$66.40	$66.40
Purchase #7	$238.62	9.756%	$261.8998	$261.90	$261.90	$261.90
7 purchase totals =	$822.38		$907.5864	$907.60	$907.60	$907.60