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	$173.34	11.478%	$193.236	$193.24	$193.25	$193.20
Purchase #2	$92.52	13.509%	$105.0185	$105.02	$105.00	$105.00
Purchase #3	$89.36	11.237%	$99.4014	$99.40	$99.40	$99.40
Purchase #4	$108.41	13.838%	$123.4118	$123.41	$123.40	$123.40
Purchase #5	$239.37	4.226%	$249.4858	$249.49	$249.50	$249.50
Purchase #6	$63.51	4.798%	$66.5572	$66.56	$66.55	$66.60
Purchase #7	$228.73	4.407%	$238.8101	$238.81	$238.80	$238.80
7 purchase totals =	$995.24		$1,075.9208	$1,075.93	$1,075.90	$1,075.90