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	$130.66	8.268%	$141.463	$141.46	$141.45	$141.50
Purchase #2	$165.88	13.105%	$187.6186	$187.62	$187.60	$187.60
Purchase #3	$160.76	9.658%	$176.2862	$176.29	$176.30	$176.30
Purchase #4	$108.89	9.755%	$119.5122	$119.51	$119.50	$119.50
Purchase #5	$240.88	5.464%	$254.0417	$254.04	$254.05	$254.00
Purchase #6	$210.93	3.491%	$218.2936	$218.29	$218.30	$218.30
Purchase #7	$43.61	9.356%	$47.6902	$47.69	$47.70	$47.70
7 purchase totals =	$1,061.61		$1,144.9055	$1,144.90	$1,144.90	$1,144.90