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	$213.73	4.261%	$222.837	$222.84	$222.85	$222.80
Purchase #2	$50.43	7.265%	$54.0937	$54.09	$54.10	$54.10
Purchase #3	$187.26	4.706%	$196.0725	$196.07	$196.05	$196.10
Purchase #4	$129.52	11.660%	$144.622	$144.62	$144.60	$144.60
Purchase #5	$183.77	12.159%	$206.1146	$206.11	$206.10	$206.10
Purchase #6	$109.86	11.798%	$122.8213	$122.82	$122.80	$122.80
Purchase #7	$122.97	9.632%	$134.8145	$134.81	$134.80	$134.80
7 purchase totals =	$997.54		$1,081.3756	$1,081.36	$1,081.30	$1,081.30