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	$176.84	4.837%	$185.3938	$185.39	$185.40	$185.40
Purchase #2	$47.95	3.223%	$49.4954	$49.50	$49.50	$49.50
Purchase #3	$108.81	7.441%	$116.9066	$116.91	$116.90	$116.90
Purchase #4	$160.45	13.745%	$182.5039	$182.50	$182.50	$182.50
Purchase #5	$218.31	10.393%	$240.999	$241.00	$241.00	$241.00
Purchase #6	$100.52	13.361%	$113.9505	$113.95	$113.95	$114.00
Purchase #7	$55.80	7.366%	$59.9102	$59.91	$59.90	$59.90
7 purchase totals =	$868.68		$949.1594	$949.16	$949.15	$949.20