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	$195.66	11.209%	$217.5915	$217.59	$217.60	$217.60
Purchase #2	$20.27	6.701%	$21.6283	$21.63	$21.65	$21.60
Purchase #3	$109.72	4.529%	$114.6892	$114.69	$114.70	$114.70
Purchase #4	$96.81	7.747%	$104.3099	$104.31	$104.30	$104.30
Purchase #5	$214.69	5.757%	$227.0497	$227.05	$227.05	$227.00
Purchase #6	$218.80	6.748%	$233.5646	$233.56	$233.55	$233.60
Purchase #7	$38.37	9.667%	$42.0792	$42.08	$42.10	$42.10
7 purchase totals =	$894.32		$960.9124	$960.91	$960.95	$960.90