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	$157.59	7.212%	$168.9554	$168.96	$168.95	$169.00
Purchase #2	$241.31	10.328%	$266.2325	$266.23	$266.25	$266.20
Purchase #3	$145.34	9.183%	$158.6866	$158.69	$158.70	$158.70
Purchase #4	$162.98	6.611%	$173.7546	$173.75	$173.75	$173.80
Purchase #5	$61.61	9.405%	$67.4044	$67.40	$67.40	$67.40
Purchase #6	$37.77	4.509%	$39.473	$39.47	$39.45	$39.50
Purchase #7	$68.63	5.182%	$72.1864	$72.19	$72.20	$72.20
7 purchase totals =	$875.23		$946.6929	$946.69	$946.70	$946.80