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	$111.28	10.161%	$122.5872	$122.59	$122.60	$122.60
Purchase #2	$69.41	12.552%	$78.1223	$78.12	$78.10	$78.10
Purchase #3	$95.72	5.546%	$101.0286	$101.03	$101.05	$101.00
Purchase #4	$69.78	9.771%	$76.5982	$76.60	$76.60	$76.60
Purchase #5	$73.66	6.486%	$78.4376	$78.44	$78.45	$78.40
Purchase #6	$241.92	9.509%	$264.9242	$264.92	$264.90	$264.90
Purchase #7	$200.90	5.239%	$211.4252	$211.43	$211.45	$211.40
7 purchase totals =	$862.67		$933.1233	$933.13	$933.15	$933.00