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	$45.69	6.301%	$48.5689	$48.57	$48.55	$48.60
Purchase #2	$68.75	13.856%	$78.276	$78.28	$78.30	$78.30
Purchase #3	$85.97	4.256%	$89.6289	$89.63	$89.65	$89.60
Purchase #4	$59.98	10.198%	$66.0968	$66.10	$66.10	$66.10
Purchase #5	$150.33	13.109%	$170.0368	$170.04	$170.05	$170.00
Purchase #6	$9.67	4.759%	$10.1302	$10.13	$10.15	$10.10
Purchase #7	$62.95	9.380%	$68.8547	$68.85	$68.85	$68.90
7 purchase totals =	$483.34		$531.5923	$531.60	$531.65	$531.60