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	$227.50	7.221%	$243.9278	$243.93	$243.95	$243.90
Purchase #2	$146.60	7.343%	$157.3648	$157.36	$157.35	$157.40
Purchase #3	$75.38	5.244%	$79.3329	$79.33	$79.35	$79.30
Purchase #4	$148.93	10.647%	$164.7866	$164.79	$164.80	$164.80
Purchase #5	$104.32	6.479%	$111.0789	$111.08	$111.10	$111.10
Purchase #6	$143.69	5.221%	$151.1921	$151.19	$151.20	$151.20
Purchase #7	$24.44	4.383%	$25.5112	$25.51	$25.50	$25.50
7 purchase totals =	$870.86		$933.1943	$933.19	$933.25	$933.20