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	$187.58	4.822%	$196.6251	$196.63	$196.65	$196.60
Purchase #2	$65.32	11.863%	$73.0689	$73.07	$73.05	$73.10
Purchase #3	$57.59	10.636%	$63.7153	$63.72	$63.70	$63.70
Purchase #4	$34.38	6.444%	$36.5954	$36.60	$36.60	$36.60
Purchase #5	$80.71	10.439%	$89.1353	$89.14	$89.15	$89.10
Purchase #6	$202.93	9.434%	$222.0744	$222.07	$222.05	$222.10
Purchase #7	$37.98	5.547%	$40.0868	$40.09	$40.10	$40.10
7 purchase totals =	$666.49		$721.3012	$721.32	$721.30	$721.30