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	$223.37	12.491%	$251.2711	$251.27	$251.25	$251.30
Purchase #2	$87.99	12.697%	$99.1621	$99.16	$99.15	$99.20
Purchase #3	$227.50	13.697%	$258.6607	$258.66	$258.65	$258.70
Purchase #4	$56.82	5.500%	$59.9451	$59.95	$59.95	$59.90
Purchase #5	$112.81	3.251%	$116.4775	$116.48	$116.50	$116.50
Purchase #6	$175.44	7.861%	$189.2313	$189.23	$189.25	$189.20
Purchase #7	$163.41	7.757%	$176.0857	$176.09	$176.10	$176.10
7 purchase totals =	$1,047.34		$1,150.8335	$1,150.84	$1,150.85	$1,150.90