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	$171.95	7.309%	$184.5178	$184.52	$184.50	$184.50
Purchase #2	$46.96	10.522%	$51.9011	$51.90	$51.90	$51.90
Purchase #3	$59.56	6.859%	$63.6452	$63.65	$63.65	$63.60
Purchase #4	$227.60	9.346%	$248.8715	$248.87	$248.85	$248.90
Purchase #5	$80.90	7.364%	$86.8575	$86.86	$86.85	$86.90
Purchase #6	$124.85	6.435%	$132.8841	$132.88	$132.90	$132.90
Purchase #7	$77.90	7.193%	$83.5033	$83.50	$83.50	$83.50
7 purchase totals =	$789.72		$852.1805	$852.18	$852.15	$852.20