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	$164.31	4.770%	$172.1476	$172.15	$172.15	$172.10
Purchase #2	$22.66	8.446%	$24.5739	$24.57	$24.55	$24.60
Purchase #3	$108.40	4.311%	$113.0731	$113.07	$113.05	$113.10
Purchase #4	$13.98	13.172%	$15.8214	$15.82	$15.80	$15.80
Purchase #5	$99.88	5.757%	$105.6301	$105.63	$105.65	$105.60
Purchase #6	$94.73	13.709%	$107.7165	$107.72	$107.70	$107.70
Purchase #7	$144.82	5.770%	$153.1761	$153.18	$153.20	$153.20
7 purchase totals =	$648.78		$692.1387	$692.14	$692.10	$692.10