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	$138.93	8.738%	$151.0697	$151.07	$151.05	$151.10
Purchase #2	$132.72	5.170%	$139.5816	$139.58	$139.60	$139.60
Purchase #3	$183.81	12.348%	$206.5069	$206.51	$206.50	$206.50
Purchase #4	$188.46	7.716%	$203.0016	$203.00	$203.00	$203.00
Purchase #5	$78.59	5.339%	$82.7859	$82.79	$82.80	$82.80
Purchase #6	$108.63	5.256%	$114.3396	$114.34	$114.35	$114.30
Purchase #7	$44.84	12.858%	$50.6055	$50.61	$50.60	$50.60
7 purchase totals =	$875.98		$947.8908	$947.90	$947.90	$947.90