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	$213.81	13.550%	$242.7813	$242.78	$242.80	$242.80
Purchase #2	$187.98	12.561%	$211.5922	$211.59	$211.60	$211.60
Purchase #3	$164.28	6.606%	$175.1323	$175.13	$175.15	$175.10
Purchase #4	$41.77	6.483%	$44.4779	$44.48	$44.50	$44.50
Purchase #5	$144.25	6.703%	$153.9191	$153.92	$153.90	$153.90
Purchase #6	$104.33	10.493%	$115.2773	$115.28	$115.30	$115.30
Purchase #7	$158.29	4.770%	$165.8404	$165.84	$165.85	$165.80
7 purchase totals =	$1,014.71		$1,109.0205	$1,109.02	$1,109.10	$1,109.00