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	$65.88	4.259%	$68.6858	$68.69	$68.70	$68.70
Purchase #2	$20.67	3.850%	$21.4658	$21.47	$21.45	$21.50
Purchase #3	$140.65	8.410%	$152.4787	$152.48	$152.50	$152.50
Purchase #4	$176.94	13.332%	$200.5296	$200.53	$200.55	$200.50
Purchase #5	$53.66	12.656%	$60.4512	$60.45	$60.45	$60.50
Purchase #6	$240.82	11.278%	$267.9797	$267.98	$268.00	$268.00
Purchase #7	$98.86	5.170%	$103.9711	$103.97	$103.95	$104.00
7 purchase totals =	$797.48		$875.5619	$875.57	$875.60	$875.70