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	$164.36	11.361%	$183.0329	$183.03	$183.05	$183.00
Purchase #2	$226.55	13.422%	$256.9575	$256.96	$256.95	$257.00
Purchase #3	$10.51	10.721%	$11.6368	$11.64	$11.65	$11.60
Purchase #4	$200.53	9.443%	$219.466	$219.47	$219.45	$219.50
Purchase #5	$156.89	5.518%	$165.5472	$165.55	$165.55	$165.50
Purchase #6	$98.32	7.127%	$105.3273	$105.33	$105.35	$105.30
Purchase #7	$25.47	8.232%	$27.5667	$27.57	$27.55	$27.60
7 purchase totals =	$882.63		$969.5344	$969.55	$969.55	$969.50