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	$179.66	3.168%	$185.3516	$185.35	$185.35	$185.40
Purchase #2	$240.79	10.342%	$265.6925	$265.69	$265.70	$265.70
Purchase #3	$56.60	10.617%	$62.6092	$62.61	$62.60	$62.60
Purchase #4	$246.51	3.459%	$255.0368	$255.04	$255.05	$255.00
Purchase #5	$149.51	7.140%	$160.185	$160.19	$160.20	$160.20
Purchase #6	$42.45	4.584%	$44.3959	$44.40	$44.40	$44.40
Purchase #7	$123.47	12.161%	$138.4852	$138.49	$138.50	$138.50
7 purchase totals =	$1,038.99		$1,111.7562	$1,111.77	$1,111.80	$1,111.80