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	$204.35	10.847%	$226.5158	$226.52	$226.50	$226.50
Purchase #2	$175.63	4.483%	$183.5035	$183.50	$183.50	$183.50
Purchase #3	$221.77	7.704%	$238.8552	$238.86	$238.85	$238.90
Purchase #4	$38.93	3.721%	$40.3786	$40.38	$40.40	$40.40
Purchase #5	$143.85	5.818%	$152.2192	$152.22	$152.20	$152.20
Purchase #6	$59.40	10.479%	$65.6245	$65.62	$65.60	$65.60
Purchase #7	$37.32	4.113%	$38.855	$38.86	$38.85	$38.90
7 purchase totals =	$881.25		$945.9518	$945.96	$945.90	$946.00