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	$42.28	3.725%	$43.8549	$43.85	$43.85	$43.90
Purchase #2	$74.92	11.685%	$83.6744	$83.67	$83.65	$83.70
Purchase #3	$40.81	12.396%	$45.8688	$45.87	$45.85	$45.90
Purchase #4	$37.35	7.810%	$40.267	$40.27	$40.25	$40.30
Purchase #5	$104.63	6.623%	$111.5596	$111.56	$111.55	$111.60
Purchase #6	$193.25	6.207%	$205.245	$205.25	$205.25	$205.20
Purchase #7	$114.54	5.812%	$121.1971	$121.20	$121.20	$121.20
7 purchase totals =	$607.78		$651.6668	$651.67	$651.60	$651.80