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	$114.79	7.298%	$123.1674	$123.17	$123.15	$123.20
Purchase #2	$103.38	7.737%	$111.3785	$111.38	$111.40	$111.40
Purchase #3	$32.68	3.138%	$33.7055	$33.71	$33.70	$33.70
Purchase #4	$164.31	8.660%	$178.5392	$178.54	$178.55	$178.50
Purchase #5	$204.26	5.282%	$215.049	$215.05	$215.05	$215.00
Purchase #6	$243.70	5.278%	$256.5625	$256.56	$256.55	$256.60
Purchase #7	$48.93	11.595%	$54.6034	$54.60	$54.60	$54.60
7 purchase totals =	$912.05		$973.0055	$973.01	$973.00	$973.00