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	$229.45	13.564%	$260.5726	$260.57	$260.55	$260.60
Purchase #2	$46.88	7.451%	$50.373	$50.37	$50.35	$50.40
Purchase #3	$72.92	11.285%	$81.149	$81.15	$81.15	$81.10
Purchase #4	$105.89	4.856%	$111.032	$111.03	$111.05	$111.00
Purchase #5	$216.60	8.431%	$234.8615	$234.86	$234.85	$234.90
Purchase #6	$181.47	8.495%	$196.8859	$196.89	$196.90	$196.90
Purchase #7	$101.68	10.392%	$112.2466	$112.25	$112.25	$112.20
7 purchase totals =	$954.89		$1,047.1206	$1,047.12	$1,047.10	$1,047.10