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	$213.99	7.422%	$229.8723	$229.87	$229.85	$229.90
Purchase #2	$122.55	12.416%	$137.7658	$137.77	$137.75	$137.80
Purchase #3	$241.50	8.471%	$261.9575	$261.96	$261.95	$262.00
Purchase #4	$164.65	10.208%	$181.4575	$181.46	$181.45	$181.50
Purchase #5	$93.29	11.141%	$103.6834	$103.68	$103.70	$103.70
Purchase #6	$13.72	12.402%	$15.4216	$15.42	$15.40	$15.40
Purchase #7	$84.38	5.482%	$89.0057	$89.01	$89.00	$89.00
7 purchase totals =	$934.08		$1,019.1638	$1,019.17	$1,019.10	$1,019.30