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	$178.26	5.660%	$188.3495	$188.35	$188.35	$188.30
Purchase #2	$222.66	8.474%	$241.5282	$241.53	$241.55	$241.50
Purchase #3	$81.38	10.264%	$89.7328	$89.73	$89.75	$89.70
Purchase #4	$40.87	7.628%	$43.9876	$43.99	$44.00	$44.00
Purchase #5	$172.67	10.477%	$190.7606	$190.76	$190.75	$190.80
Purchase #6	$97.85	7.739%	$105.4226	$105.42	$105.40	$105.40
Purchase #7	$124.36	13.268%	$140.8601	$140.86	$140.85	$140.90
7 purchase totals =	$918.05		$1,000.6414	$1,000.64	$1,000.65	$1,000.60