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	$99.81	3.632%	$103.4351	$103.44	$103.45	$103.40
Purchase #2	$148.59	9.151%	$162.1875	$162.19	$162.20	$162.20
Purchase #3	$95.60	12.306%	$107.3645	$107.36	$107.35	$107.40
Purchase #4	$99.45	12.380%	$111.7619	$111.76	$111.75	$111.80
Purchase #5	$163.71	6.223%	$173.8977	$173.90	$173.90	$173.90
Purchase #6	$99.80	13.807%	$113.5794	$113.58	$113.60	$113.60
Purchase #7	$147.71	6.452%	$157.2402	$157.24	$157.25	$157.20
7 purchase totals =	$854.67		$929.4663	$929.47	$929.50	$929.50