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	$138.64	5.105%	$145.7176	$145.72	$145.70	$145.70
Purchase #2	$161.39	8.264%	$174.7273	$174.73	$174.75	$174.70
Purchase #3	$72.71	4.540%	$76.011	$76.01	$76.00	$76.00
Purchase #4	$168.64	3.275%	$174.163	$174.16	$174.15	$174.20
Purchase #5	$151.83	12.325%	$170.543	$170.54	$170.55	$170.50
Purchase #6	$50.77	3.844%	$52.7216	$52.72	$52.70	$52.70
Purchase #7	$102.96	6.395%	$109.5443	$109.54	$109.55	$109.50
7 purchase totals =	$846.94		$903.4278	$903.42	$903.40	$903.30