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	$64.59	12.529%	$72.6825	$72.68	$72.70	$72.70
Purchase #2	$211.89	3.551%	$219.4142	$219.41	$219.40	$219.40
Purchase #3	$216.92	5.443%	$228.727	$228.73	$228.75	$228.70
Purchase #4	$42.74	4.315%	$44.5842	$44.58	$44.60	$44.60
Purchase #5	$241.81	5.666%	$255.511	$255.51	$255.50	$255.50
Purchase #6	$83.25	8.509%	$90.3337	$90.33	$90.35	$90.30
Purchase #7	$208.57	12.302%	$234.2283	$234.23	$234.25	$234.20
7 purchase totals =	$1,069.77		$1,145.4809	$1,145.47	$1,145.55	$1,145.40