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	$63.69	4.672%	$66.6656	$66.67	$66.65	$66.70
Purchase #2	$151.83	11.825%	$169.7839	$169.78	$169.80	$169.80
Purchase #3	$201.73	11.698%	$225.3284	$225.33	$225.35	$225.30
Purchase #4	$175.98	4.852%	$184.5185	$184.52	$184.50	$184.50
Purchase #5	$74.56	5.402%	$78.5877	$78.59	$78.60	$78.60
Purchase #6	$12.74	9.256%	$13.9192	$13.92	$13.90	$13.90
Purchase #7	$49.25	5.362%	$51.8908	$51.89	$51.90	$51.90
7 purchase totals =	$729.78		$790.6941	$790.70	$790.70	$790.70