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	$211.99	7.604%	$228.1097	$228.11	$228.10	$228.10
Purchase #2	$85.83	5.124%	$90.2279	$90.23	$90.25	$90.20
Purchase #3	$136.57	13.504%	$155.0124	$155.01	$155.00	$155.00
Purchase #4	$108.25	3.447%	$111.9814	$111.98	$112.00	$112.00
Purchase #5	$240.37	13.272%	$272.2719	$272.27	$272.25	$272.30
Purchase #6	$99.94	8.176%	$108.1111	$108.11	$108.10	$108.10
Purchase #7	$14.40	5.208%	$15.15	$15.15	$15.15	$15.20
7 purchase totals =	$897.35		$980.8644	$980.86	$980.85	$980.90