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	$105.80	6.514%	$112.6918	$112.69	$112.70	$112.70
Purchase #2	$215.88	8.248%	$233.6858	$233.69	$233.70	$233.70
Purchase #3	$92.51	12.239%	$103.8323	$103.83	$103.85	$103.80
Purchase #4	$60.64	7.488%	$65.1807	$65.18	$65.20	$65.20
Purchase #5	$160.89	8.443%	$174.4739	$174.47	$174.45	$174.50
Purchase #6	$203.63	13.234%	$230.5784	$230.58	$230.60	$230.60
Purchase #7	$86.25	3.640%	$89.3895	$89.39	$89.40	$89.40
7 purchase totals =	$925.60		$1,009.8324	$1,009.83	$1,009.90	$1,009.90