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	$208.54	8.512%	$226.2909	$226.29	$226.30	$226.30
Purchase #2	$156.66	10.124%	$172.5203	$172.52	$172.50	$172.50
Purchase #3	$186.39	11.772%	$208.3318	$208.33	$208.35	$208.30
Purchase #4	$168.59	8.752%	$183.345	$183.35	$183.35	$183.30
Purchase #5	$133.77	5.321%	$140.8879	$140.89	$140.90	$140.90
Purchase #6	$78.89	10.798%	$87.4085	$87.41	$87.40	$87.40
Purchase #7	$119.49	6.641%	$127.4253	$127.43	$127.45	$127.40
7 purchase totals =	$1,052.33		$1,146.2097	$1,146.22	$1,146.25	$1,146.10