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	$164.59	5.697%	$173.9667	$173.97	$173.95	$174.00
Purchase #2	$40.76	6.176%	$43.2773	$43.28	$43.30	$43.30
Purchase #3	$96.93	7.580%	$104.2773	$104.28	$104.30	$104.30
Purchase #4	$136.31	7.269%	$146.2184	$146.22	$146.20	$146.20
Purchase #5	$198.51	3.854%	$206.1606	$206.16	$206.15	$206.20
Purchase #6	$187.89	4.788%	$196.8862	$196.89	$196.90	$196.90
Purchase #7	$91.55	8.811%	$99.6165	$99.62	$99.60	$99.60
7 purchase totals =	$916.54		$970.4030	$970.42	$970.40	$970.50