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	$244.48	6.684%	$260.821	$260.82	$260.80	$260.80
Purchase #2	$50.81	11.320%	$56.5617	$56.56	$56.55	$56.60
Purchase #3	$193.37	11.451%	$215.5128	$215.51	$215.50	$215.50
Purchase #4	$182.28	4.661%	$190.7761	$190.78	$190.80	$190.80
Purchase #5	$16.48	8.460%	$17.8742	$17.87	$17.85	$17.90
Purchase #6	$231.33	4.594%	$241.9573	$241.96	$241.95	$242.00
Purchase #7	$94.38	7.595%	$101.5482	$101.55	$101.55	$101.50
7 purchase totals =	$1,013.13		$1,085.0513	$1,085.05	$1,085.00	$1,085.10