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	$57.64	12.128%	$64.6306	$64.63	$64.65	$64.60
Purchase #2	$241.44	12.780%	$272.296	$272.30	$272.30	$272.30
Purchase #3	$243.79	5.169%	$256.3915	$256.39	$256.40	$256.40
Purchase #4	$175.89	11.797%	$196.6397	$196.64	$196.65	$196.60
Purchase #5	$79.31	10.392%	$87.5519	$87.55	$87.55	$87.60
Purchase #6	$118.47	6.274%	$125.9028	$125.90	$125.90	$125.90
Purchase #7	$90.85	5.212%	$95.5851	$95.59	$95.60	$95.60
7 purchase totals =	$1,007.39		$1,098.9976	$1,099.00	$1,099.05	$1,099.00