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	$46.50	13.221%	$52.6478	$52.65	$52.65	$52.60
Purchase #2	$126.88	12.584%	$142.8466	$142.85	$142.85	$142.80
Purchase #3	$137.47	10.623%	$152.0734	$152.07	$152.05	$152.10
Purchase #4	$198.75	10.259%	$219.1398	$219.14	$219.15	$219.10
Purchase #5	$241.49	13.832%	$274.8929	$274.89	$274.90	$274.90
Purchase #6	$153.93	12.698%	$173.476	$173.48	$173.50	$173.50
Purchase #7	$6.45	11.843%	$7.2139	$7.21	$7.20	$7.20
7 purchase totals =	$911.47		$1,022.2904	$1,022.29	$1,022.30	$1,022.20