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	$11.65	5.359%	$12.2743	$12.27	$12.25	$12.30
Purchase #2	$182.87	6.649%	$195.029	$195.03	$195.05	$195.00
Purchase #3	$124.46	5.583%	$131.4086	$131.41	$131.40	$131.40
Purchase #4	$87.62	13.449%	$99.404	$99.40	$99.40	$99.40
Purchase #5	$231.85	4.568%	$242.4409	$242.44	$242.45	$242.40
Purchase #6	$69.67	12.798%	$78.5864	$78.59	$78.60	$78.60
Purchase #7	$135.46	9.311%	$148.0727	$148.07	$148.05	$148.10
7 purchase totals =	$843.58		$907.2159	$907.21	$907.20	$907.20