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	$152.86	3.513%	$158.23	$158.23	$158.25	$158.20
Purchase #2	$119.90	7.172%	$128.4992	$128.50	$128.50	$128.50
Purchase #3	$75.55	13.697%	$85.8981	$85.90	$85.90	$85.90
Purchase #4	$249.45	8.713%	$271.1846	$271.18	$271.20	$271.20
Purchase #5	$105.86	5.855%	$112.0581	$112.06	$112.05	$112.10
Purchase #6	$26.28	5.681%	$27.773	$27.77	$27.75	$27.80
Purchase #7	$145.93	9.269%	$159.4563	$159.46	$159.45	$159.50
7 purchase totals =	$875.83		$943.0993	$943.10	$943.10	$943.20