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	$162.82	5.249%	$171.3664	$171.37	$171.35	$171.40
Purchase #2	$171.73	13.239%	$194.4653	$194.47	$194.45	$194.50
Purchase #3	$172.54	7.278%	$185.0975	$185.10	$185.10	$185.10
Purchase #4	$74.61	4.469%	$77.9443	$77.94	$77.95	$77.90
Purchase #5	$232.64	5.464%	$245.3514	$245.35	$245.35	$245.40
Purchase #6	$117.78	11.738%	$131.605	$131.61	$131.60	$131.60
Purchase #7	$230.98	4.463%	$241.2886	$241.29	$241.30	$241.30
7 purchase totals =	$1,163.10		$1,247.1185	$1,247.13	$1,247.10	$1,247.20