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	$90.81	7.337%	$97.4727	$97.47	$97.45	$97.50
Purchase #2	$133.60	7.163%	$143.1698	$143.17	$143.15	$143.20
Purchase #3	$213.98	13.240%	$242.311	$242.31	$242.30	$242.30
Purchase #4	$233.36	9.530%	$255.5992	$255.60	$255.60	$255.60
Purchase #5	$57.99	12.355%	$65.1547	$65.15	$65.15	$65.20
Purchase #6	$53.56	11.548%	$59.7451	$59.75	$59.75	$59.70
Purchase #7	$128.41	9.842%	$141.0481	$141.05	$141.05	$141.00
7 purchase totals =	$911.71		$1,004.5006	$1,004.50	$1,004.45	$1,004.50