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	$101.51	9.556%	$111.2103	$111.21	$111.20	$111.20
Purchase #2	$205.60	11.811%	$229.8834	$229.88	$229.90	$229.90
Purchase #3	$249.35	4.624%	$260.8799	$260.88	$260.90	$260.90
Purchase #4	$228.51	10.646%	$252.8372	$252.84	$252.85	$252.80
Purchase #5	$41.92	8.518%	$45.4907	$45.49	$45.50	$45.50
Purchase #6	$165.25	6.199%	$175.4938	$175.49	$175.50	$175.50
Purchase #7	$151.45	5.851%	$160.3113	$160.31	$160.30	$160.30
7 purchase totals =	$1,143.59		$1,236.1066	$1,236.10	$1,236.15	$1,236.10