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	$99.69	7.852%	$107.5177	$107.52	$107.50	$107.50
Purchase #2	$143.89	13.705%	$163.6101	$163.61	$163.60	$163.60
Purchase #3	$164.79	13.201%	$186.5439	$186.54	$186.55	$186.50
Purchase #4	$214.61	6.213%	$227.9437	$227.94	$227.95	$227.90
Purchase #5	$81.63	9.321%	$89.2387	$89.24	$89.25	$89.20
Purchase #6	$98.81	12.812%	$111.4695	$111.47	$111.45	$111.50
Purchase #7	$162.81	6.788%	$173.8615	$173.86	$173.85	$173.90
7 purchase totals =	$966.23		$1,060.1851	$1,060.18	$1,060.15	$1,060.10