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	$83.84	10.453%	$92.6038	$92.60	$92.60	$92.60
Purchase #2	$10.99	13.377%	$12.4601	$12.46	$12.45	$12.50
Purchase #3	$200.84	9.289%	$219.496	$219.50	$219.50	$219.50
Purchase #4	$82.87	10.291%	$91.3982	$91.40	$91.40	$91.40
Purchase #5	$78.85	3.522%	$81.6271	$81.63	$81.65	$81.60
Purchase #6	$101.95	11.284%	$113.454	$113.45	$113.45	$113.50
Purchase #7	$47.94	13.171%	$54.2542	$54.25	$54.25	$54.30
7 purchase totals =	$607.28		$665.2934	$665.29	$665.30	$665.40