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	$168.43	12.487%	$189.4619	$189.46	$189.45	$189.50
Purchase #2	$54.29	4.651%	$56.815	$56.82	$56.80	$56.80
Purchase #3	$101.48	5.316%	$106.8747	$106.87	$106.85	$106.90
Purchase #4	$239.84	13.268%	$271.662	$271.66	$271.65	$271.70
Purchase #5	$181.73	8.249%	$196.7209	$196.72	$196.70	$196.70
Purchase #6	$54.57	13.641%	$62.0139	$62.01	$62.00	$62.00
Purchase #7	$174.49	10.297%	$192.4572	$192.46	$192.45	$192.50
7 purchase totals =	$974.83		$1,076.0056	$1,076.00	$1,075.90	$1,076.10