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	$73.69	5.192%	$77.516	$77.52	$77.50	$77.50
Purchase #2	$143.69	10.329%	$158.5317	$158.53	$158.55	$158.50
Purchase #3	$212.71	4.374%	$222.0139	$222.01	$222.00	$222.00
Purchase #4	$145.70	4.721%	$152.5785	$152.58	$152.60	$152.60
Purchase #5	$99.34	3.142%	$102.4613	$102.46	$102.45	$102.50
Purchase #6	$230.93	13.391%	$261.8538	$261.85	$261.85	$261.90
Purchase #7	$180.28	11.431%	$200.8878	$200.89	$200.90	$200.90
7 purchase totals =	$1,086.34		$1,175.8430	$1,175.84	$1,175.85	$1,175.90