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	$109.87	3.222%	$113.41	$113.41	$113.40	$113.40
Purchase #2	$225.97	5.151%	$237.6097	$237.61	$237.60	$237.60
Purchase #3	$193.28	3.176%	$199.4186	$199.42	$199.40	$199.40
Purchase #4	$70.76	10.627%	$78.2797	$78.28	$78.30	$78.30
Purchase #5	$205.73	13.732%	$233.9808	$233.98	$234.00	$234.00
Purchase #6	$100.85	11.347%	$112.2934	$112.29	$112.30	$112.30
Purchase #7	$123.72	7.195%	$132.6217	$132.62	$132.60	$132.60
7 purchase totals =	$1,030.18		$1,107.6139	$1,107.61	$1,107.60	$1,107.60