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	$225.88	6.437%	$240.4199	$240.42	$240.40	$240.40
Purchase #2	$89.72	13.430%	$101.7694	$101.77	$101.75	$101.80
Purchase #3	$172.88	13.555%	$196.3139	$196.31	$196.30	$196.30
Purchase #4	$213.27	7.142%	$228.5017	$228.50	$228.50	$228.50
Purchase #5	$10.72	3.629%	$11.109	$11.11	$11.10	$11.10
Purchase #6	$138.60	10.544%	$153.214	$153.21	$153.20	$153.20
Purchase #7	$9.95	4.580%	$10.4057	$10.41	$10.40	$10.40
7 purchase totals =	$861.02		$941.7336	$941.73	$941.65	$941.70