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	$248.45	4.783%	$260.3334	$260.33	$260.35	$260.30
Purchase #2	$228.57	12.349%	$256.7961	$256.80	$256.80	$256.80
Purchase #3	$111.81	3.126%	$115.3052	$115.31	$115.30	$115.30
Purchase #4	$210.50	13.648%	$239.229	$239.23	$239.25	$239.20
Purchase #5	$127.55	4.109%	$132.791	$132.79	$132.80	$132.80
Purchase #6	$62.25	5.346%	$65.5779	$65.58	$65.60	$65.60
Purchase #7	$55.27	7.598%	$59.4694	$59.47	$59.45	$59.50
7 purchase totals =	$1,044.40		$1,129.5020	$1,129.51	$1,129.55	$1,129.50