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	$128.88	12.639%	$145.1691	$145.17	$145.15	$145.20
Purchase #2	$152.94	9.810%	$167.9434	$167.94	$167.95	$167.90
Purchase #3	$38.40	13.507%	$43.5867	$43.59	$43.60	$43.60
Purchase #4	$155.97	11.262%	$173.5353	$173.54	$173.55	$173.50
Purchase #5	$54.79	5.811%	$57.9738	$57.97	$57.95	$58.00
Purchase #6	$113.58	12.798%	$128.116	$128.12	$128.10	$128.10
Purchase #7	$74.57	4.741%	$78.1054	$78.11	$78.10	$78.10
7 purchase totals =	$719.13		$794.4297	$794.44	$794.40	$794.40