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	$40.50	10.861%	$44.8987	$44.90	$44.90	$44.90
Purchase #2	$168.78	13.777%	$192.0328	$192.03	$192.05	$192.00
Purchase #3	$36.44	3.687%	$37.7835	$37.78	$37.80	$37.80
Purchase #4	$233.73	13.359%	$264.954	$264.95	$264.95	$265.00
Purchase #5	$51.83	10.813%	$57.4344	$57.43	$57.45	$57.40
Purchase #6	$230.74	13.692%	$262.3329	$262.33	$262.35	$262.30
Purchase #7	$29.51	10.235%	$32.5303	$32.53	$32.55	$32.50
7 purchase totals =	$791.53		$891.9666	$891.95	$892.05	$891.90