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	$90.50	5.435%	$95.4187	$95.42	$95.40	$95.40
Purchase #2	$222.83	4.578%	$233.0312	$233.03	$233.05	$233.00
Purchase #3	$226.27	9.430%	$247.6073	$247.61	$247.60	$247.60
Purchase #4	$207.48	13.185%	$234.8362	$234.84	$234.85	$234.80
Purchase #5	$72.99	12.115%	$81.8327	$81.83	$81.85	$81.80
Purchase #6	$56.73	4.165%	$59.0928	$59.09	$59.10	$59.10
Purchase #7	$22.45	10.622%	$24.8346	$24.83	$24.85	$24.80
7 purchase totals =	$899.25		$976.6535	$976.65	$976.70	$976.50