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	$55.51	12.276%	$62.3244	$62.32	$62.30	$62.30
Purchase #2	$250.80	12.524%	$282.2102	$282.21	$282.20	$282.20
Purchase #3	$45.52	12.842%	$51.3657	$51.37	$51.35	$51.40
Purchase #4	$48.47	13.650%	$55.0862	$55.09	$55.10	$55.10
Purchase #5	$10.76	3.769%	$11.1655	$11.17	$11.15	$11.20
Purchase #6	$233.67	5.393%	$246.2718	$246.27	$246.25	$246.30
Purchase #7	$162.28	6.527%	$172.872	$172.87	$172.85	$172.90
7 purchase totals =	$807.01		$881.2958	$881.30	$881.20	$881.40