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	$17.94	10.284%	$19.7849	$19.78	$19.80	$19.80
Purchase #2	$106.35	5.652%	$112.3609	$112.36	$112.35	$112.40
Purchase #3	$244.72	12.724%	$275.8582	$275.86	$275.85	$275.90
Purchase #4	$167.60	8.424%	$181.7186	$181.72	$181.70	$181.70
Purchase #5	$207.46	7.632%	$223.2933	$223.29	$223.30	$223.30
Purchase #6	$41.88	8.830%	$45.578	$45.58	$45.60	$45.60
Purchase #7	$90.54	5.387%	$95.4174	$95.42	$95.40	$95.40
7 purchase totals =	$876.49		$954.0113	$954.01	$954.00	$954.10