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	$15.59	10.638%	$17.2485	$17.25	$17.25	$17.20
Purchase #2	$113.41	9.246%	$123.8959	$123.90	$123.90	$123.90
Purchase #3	$46.90	11.364%	$52.2297	$52.23	$52.25	$52.20
Purchase #4	$141.83	7.728%	$152.7906	$152.79	$152.80	$152.80
Purchase #5	$45.56	6.662%	$48.5952	$48.60	$48.60	$48.60
Purchase #6	$109.28	5.202%	$114.9647	$114.96	$114.95	$115.00
Purchase #7	$154.84	12.337%	$173.9426	$173.94	$173.95	$173.90
7 purchase totals =	$627.41		$683.6672	$683.67	$683.70	$683.60