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	$168.31	13.781%	$191.5048	$191.50	$191.50	$191.50
Purchase #2	$132.46	7.699%	$142.6581	$142.66	$142.65	$142.70
Purchase #3	$76.79	11.731%	$85.7982	$85.80	$85.80	$85.80
Purchase #4	$102.27	13.759%	$116.3413	$116.34	$116.35	$116.30
Purchase #5	$123.29	10.644%	$136.413	$136.41	$136.40	$136.40
Purchase #6	$63.26	5.484%	$66.7292	$66.73	$66.75	$66.70
Purchase #7	$29.54	11.500%	$32.9371	$32.94	$32.95	$32.90
7 purchase totals =	$695.92		$772.3817	$772.38	$772.40	$772.30