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	$216.51	13.457%	$245.6458	$245.65	$245.65	$245.60
Purchase #2	$80.54	5.541%	$85.0027	$85.00	$85.00	$85.00
Purchase #3	$89.73	12.102%	$100.5891	$100.59	$100.60	$100.60
Purchase #4	$87.77	9.336%	$95.9642	$95.96	$95.95	$96.00
Purchase #5	$32.93	12.641%	$37.0927	$37.09	$37.10	$37.10
Purchase #6	$165.72	8.673%	$180.0929	$180.09	$180.10	$180.10
Purchase #7	$140.83	9.784%	$154.6088	$154.61	$154.60	$154.60
7 purchase totals =	$814.03		$898.9962	$898.99	$899.00	$899.00