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	$201.66	7.331%	$216.4437	$216.44	$216.45	$216.40
Purchase #2	$97.29	5.240%	$102.388	$102.39	$102.40	$102.40
Purchase #3	$138.25	3.151%	$142.6063	$142.61	$142.60	$142.60
Purchase #4	$70.80	11.324%	$78.8174	$78.82	$78.80	$78.80
Purchase #5	$182.33	5.766%	$192.8431	$192.84	$192.85	$192.80
Purchase #6	$134.69	4.789%	$141.1403	$141.14	$141.15	$141.10
Purchase #7	$118.89	4.339%	$124.0486	$124.05	$124.05	$124.00
7 purchase totals =	$943.91		$998.2874	$998.29	$998.30	$998.10