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	$230.69	9.567%	$252.7601	$252.76	$252.75	$252.80
Purchase #2	$186.95	7.488%	$200.9488	$200.95	$200.95	$200.90
Purchase #3	$101.48	9.449%	$111.0688	$111.07	$111.05	$111.10
Purchase #4	$92.59	13.502%	$105.0915	$105.09	$105.10	$105.10
Purchase #5	$205.35	8.484%	$222.7719	$222.77	$222.75	$222.80
Purchase #6	$81.79	13.538%	$92.8627	$92.86	$92.85	$92.90
Purchase #7	$158.61	6.722%	$169.2718	$169.27	$169.25	$169.30
7 purchase totals =	$1,057.46		$1,154.7756	$1,154.77	$1,154.70	$1,154.90