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	$67.38	3.464%	$69.714	$69.71	$69.70	$69.70
Purchase #2	$92.33	7.874%	$99.6001	$99.60	$99.60	$99.60
Purchase #3	$122.48	8.171%	$132.4878	$132.49	$132.50	$132.50
Purchase #4	$95.29	11.178%	$105.9415	$105.94	$105.95	$105.90
Purchase #5	$200.47	8.548%	$217.6062	$217.61	$217.60	$217.60
Purchase #6	$153.30	7.283%	$164.4648	$164.46	$164.45	$164.50
Purchase #7	$143.71	11.750%	$160.5959	$160.60	$160.60	$160.60
7 purchase totals =	$874.96		$950.4103	$950.41	$950.40	$950.40