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	$217.48	10.429%	$240.161	$240.16	$240.15	$240.20
Purchase #2	$14.27	8.669%	$15.5071	$15.51	$15.50	$15.50
Purchase #3	$16.68	11.375%	$18.5774	$18.58	$18.60	$18.60
Purchase #4	$83.30	10.330%	$91.9049	$91.90	$91.90	$91.90
Purchase #5	$123.29	8.770%	$134.1025	$134.10	$134.10	$134.10
Purchase #6	$153.29	9.162%	$167.3344	$167.33	$167.35	$167.30
Purchase #7	$40.40	11.422%	$45.0145	$45.01	$45.00	$45.00
7 purchase totals =	$648.71		$712.6018	$712.59	$712.60	$712.60