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	$224.96	8.364%	$243.7757	$243.78	$243.80	$243.80
Purchase #2	$40.69	3.684%	$42.189	$42.19	$42.20	$42.20
Purchase #3	$134.34	10.724%	$148.7466	$148.75	$148.75	$148.70
Purchase #4	$71.87	4.372%	$75.0122	$75.01	$75.00	$75.00
Purchase #5	$107.68	3.613%	$111.5705	$111.57	$111.55	$111.60
Purchase #6	$24.95	7.719%	$26.8759	$26.88	$26.90	$26.90
Purchase #7	$80.57	12.465%	$90.6131	$90.61	$90.60	$90.60
7 purchase totals =	$685.06		$738.7830	$738.79	$738.80	$738.80