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	$97.80	12.333%	$109.8617	$109.86	$109.85	$109.90
Purchase #2	$51.79	11.699%	$57.8489	$57.85	$57.85	$57.80
Purchase #3	$102.69	8.398%	$111.3139	$111.31	$111.30	$111.30
Purchase #4	$30.96	11.452%	$34.5055	$34.51	$34.50	$34.50
Purchase #5	$151.37	6.709%	$161.5254	$161.53	$161.55	$161.50
Purchase #6	$33.47	10.311%	$36.9211	$36.92	$36.90	$36.90
Purchase #7	$110.54	3.209%	$114.0872	$114.09	$114.10	$114.10
7 purchase totals =	$578.62		$626.0637	$626.07	$626.05	$626.00