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	$117.61	5.341%	$123.8916	$123.89	$123.90	$123.90
Purchase #2	$195.71	6.521%	$208.4722	$208.47	$208.45	$208.50
Purchase #3	$50.32	4.159%	$52.4128	$52.41	$52.40	$52.40
Purchase #4	$113.28	12.378%	$127.3018	$127.30	$127.30	$127.30
Purchase #5	$148.59	4.726%	$155.6124	$155.61	$155.60	$155.60
Purchase #6	$127.44	13.688%	$144.884	$144.88	$144.90	$144.90
Purchase #7	$146.88	3.844%	$152.5261	$152.53	$152.55	$152.50
7 purchase totals =	$899.83		$965.1009	$965.09	$965.10	$965.10