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	$68.62	5.491%	$72.3879	$72.39	$72.40	$72.40
Purchase #2	$41.96	5.177%	$44.1323	$44.13	$44.15	$44.10
Purchase #3	$245.32	10.316%	$270.6272	$270.63	$270.65	$270.60
Purchase #4	$145.88	5.572%	$154.0084	$154.01	$154.00	$154.00
Purchase #5	$249.77	6.329%	$265.5779	$265.58	$265.60	$265.60
Purchase #6	$107.37	3.638%	$111.2761	$111.28	$111.30	$111.30
Purchase #7	$123.28	10.489%	$136.2108	$136.21	$136.20	$136.20
7 purchase totals =	$982.20		$1,054.2206	$1,054.23	$1,054.30	$1,054.20