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	$33.59	10.871%	$37.2416	$37.24	$37.25	$37.20
Purchase #2	$40.34	7.704%	$43.4478	$43.45	$43.45	$43.40
Purchase #3	$59.38	4.189%	$61.8674	$61.87	$61.85	$61.90
Purchase #4	$99.99	11.816%	$111.8048	$111.80	$111.80	$111.80
Purchase #5	$9.81	10.694%	$10.8591	$10.86	$10.85	$10.90
Purchase #6	$230.32	3.513%	$238.4111	$238.41	$238.40	$238.40
Purchase #7	$243.51	3.259%	$251.446	$251.45	$251.45	$251.40
7 purchase totals =	$716.94		$755.0778	$755.08	$755.05	$755.00