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	$133.76	5.849%	$141.5836	$141.58	$141.60	$141.60
Purchase #2	$155.92	3.436%	$161.2774	$161.28	$161.30	$161.30
Purchase #3	$188.56	6.439%	$200.7014	$200.70	$200.70	$200.70
Purchase #4	$110.41	8.560%	$119.8611	$119.86	$119.85	$119.90
Purchase #5	$75.97	6.469%	$80.8845	$80.88	$80.90	$80.90
Purchase #6	$143.87	5.714%	$152.0907	$152.09	$152.10	$152.10
Purchase #7	$112.25	13.407%	$127.2994	$127.30	$127.30	$127.30
7 purchase totals =	$920.74		$983.6981	$983.69	$983.75	$983.80