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	$171.85	10.848%	$190.4923	$190.49	$190.50	$190.50
Purchase #2	$87.89	6.840%	$93.9017	$93.90	$93.90	$93.90
Purchase #3	$123.74	3.133%	$127.6168	$127.62	$127.60	$127.60
Purchase #4	$229.85	11.351%	$255.9403	$255.94	$255.95	$255.90
Purchase #5	$250.88	5.765%	$265.3432	$265.34	$265.35	$265.30
Purchase #6	$105.25	5.710%	$111.2598	$111.26	$111.25	$111.30
Purchase #7	$105.69	8.739%	$114.9262	$114.93	$114.95	$114.90
7 purchase totals =	$1,075.15		$1,159.4803	$1,159.48	$1,159.50	$1,159.40