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	$95.42	9.532%	$104.5154	$104.52	$104.50	$104.50
Purchase #2	$63.50	3.860%	$65.9511	$65.95	$65.95	$66.00
Purchase #3	$233.38	7.272%	$250.3514	$250.35	$250.35	$250.40
Purchase #4	$12.27	10.308%	$13.5348	$13.53	$13.55	$13.50
Purchase #5	$196.72	12.643%	$221.5913	$221.59	$221.60	$221.60
Purchase #6	$199.75	11.619%	$222.959	$222.96	$222.95	$223.00
Purchase #7	$67.77	12.809%	$76.4507	$76.45	$76.45	$76.50
7 purchase totals =	$868.81		$955.3537	$955.35	$955.35	$955.50