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	$79.26	13.127%	$89.6645	$89.66	$89.65	$89.70
Purchase #2	$43.80	11.337%	$48.7656	$48.77	$48.75	$48.80
Purchase #3	$141.36	7.431%	$151.8645	$151.86	$151.85	$151.90
Purchase #4	$50.53	12.380%	$56.7856	$56.79	$56.80	$56.80
Purchase #5	$111.84	10.558%	$123.6481	$123.65	$123.65	$123.60
Purchase #6	$241.91	9.476%	$264.8334	$264.83	$264.85	$264.80
Purchase #7	$142.54	13.307%	$161.5078	$161.51	$161.50	$161.50
7 purchase totals =	$811.24		$897.0695	$897.07	$897.05	$897.10