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	$35.42	9.153%	$38.662	$38.66	$38.65	$38.70
Purchase #2	$223.66	9.571%	$245.0665	$245.07	$245.05	$245.10
Purchase #3	$186.61	3.138%	$192.4658	$192.47	$192.45	$192.50
Purchase #4	$151.38	4.446%	$158.1104	$158.11	$158.10	$158.10
Purchase #5	$141.47	13.646%	$160.775	$160.78	$160.80	$160.80
Purchase #6	$119.72	6.297%	$127.2588	$127.26	$127.25	$127.30
Purchase #7	$224.68	7.822%	$242.2545	$242.25	$242.25	$242.30
7 purchase totals =	$1,082.94		$1,164.5930	$1,164.60	$1,164.55	$1,164.80