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	$92.70	10.160%	$102.1183	$102.12	$102.10	$102.10
Purchase #2	$169.96	5.422%	$179.1752	$179.18	$179.20	$179.20
Purchase #3	$217.88	13.725%	$247.784	$247.78	$247.80	$247.80
Purchase #4	$124.72	5.406%	$131.4624	$131.46	$131.45	$131.50
Purchase #5	$48.61	6.772%	$51.9019	$51.90	$51.90	$51.90
Purchase #6	$133.86	7.854%	$144.3734	$144.37	$144.35	$144.40
Purchase #7	$85.91	5.534%	$90.6643	$90.66	$90.65	$90.70
7 purchase totals =	$873.64		$947.4795	$947.47	$947.45	$947.60