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	$199.82	7.356%	$214.5188	$214.52	$214.50	$214.50
Purchase #2	$39.81	9.591%	$43.6282	$43.63	$43.65	$43.60
Purchase #3	$83.77	6.285%	$89.0349	$89.03	$89.05	$89.00
Purchase #4	$171.57	13.279%	$194.3528	$194.35	$194.35	$194.40
Purchase #5	$139.98	4.363%	$146.0873	$146.09	$146.10	$146.10
Purchase #6	$124.33	7.370%	$133.4931	$133.49	$133.50	$133.50
Purchase #7	$56.85	7.807%	$61.2883	$61.29	$61.30	$61.30
7 purchase totals =	$816.13		$882.4034	$882.40	$882.45	$882.40