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	$51.58	5.426%	$54.3787	$54.38	$54.40	$54.40
Purchase #2	$60.81	11.618%	$67.8749	$67.87	$67.85	$67.90
Purchase #3	$167.82	11.209%	$186.6309	$186.63	$186.65	$186.60
Purchase #4	$36.30	7.713%	$39.0998	$39.10	$39.10	$39.10
Purchase #5	$64.70	11.783%	$72.3236	$72.32	$72.30	$72.30
Purchase #6	$64.81	11.781%	$72.4453	$72.45	$72.45	$72.40
Purchase #7	$19.58	8.733%	$21.2899	$21.29	$21.30	$21.30
7 purchase totals =	$465.60		$514.0431	$514.04	$514.05	$514.00