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	$196.62	12.383%	$220.9675	$220.97	$220.95	$221.00
Purchase #2	$98.42	13.453%	$111.6604	$111.66	$111.65	$111.70
Purchase #3	$138.29	13.469%	$156.9163	$156.92	$156.90	$156.90
Purchase #4	$52.49	13.574%	$59.615	$59.62	$59.60	$59.60
Purchase #5	$241.81	3.316%	$249.8284	$249.83	$249.85	$249.80
Purchase #6	$133.59	13.613%	$151.7756	$151.78	$151.80	$151.80
Purchase #7	$143.88	10.650%	$159.2032	$159.20	$159.20	$159.20
7 purchase totals =	$1,005.10		$1,109.9664	$1,109.98	$1,109.95	$1,110.00