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	$164.39	5.711%	$173.7783	$173.78	$173.80	$173.80
Purchase #2	$167.56	7.534%	$180.184	$180.18	$180.20	$180.20
Purchase #3	$139.96	8.314%	$151.5963	$151.60	$151.60	$151.60
Purchase #4	$61.51	6.619%	$65.5813	$65.58	$65.60	$65.60
Purchase #5	$53.43	13.104%	$60.4315	$60.43	$60.45	$60.40
Purchase #6	$133.39	6.660%	$142.2738	$142.27	$142.25	$142.30
Purchase #7	$79.84	9.440%	$87.3769	$87.38	$87.40	$87.40
7 purchase totals =	$800.08		$861.2221	$861.22	$861.30	$861.30