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	$208.44	5.351%	$219.5936	$219.59	$219.60	$219.60
Purchase #2	$124.99	4.712%	$130.8795	$130.88	$130.90	$130.90
Purchase #3	$182.56	9.853%	$200.5476	$200.55	$200.55	$200.50
Purchase #4	$83.26	10.224%	$91.7725	$91.77	$91.75	$91.80
Purchase #5	$62.85	4.233%	$65.5104	$65.51	$65.50	$65.50
Purchase #6	$239.82	10.286%	$264.4879	$264.49	$264.50	$264.50
Purchase #7	$47.51	7.509%	$51.0775	$51.08	$51.10	$51.10
7 purchase totals =	$949.43		$1,023.8690	$1,023.87	$1,023.90	$1,023.90