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	$73.43	11.105%	$81.5844	$81.58	$81.60	$81.60
Purchase #2	$116.28	6.275%	$123.5766	$123.58	$123.60	$123.60
Purchase #3	$216.52	4.562%	$226.3976	$226.40	$226.40	$226.40
Purchase #4	$19.55	3.819%	$20.2966	$20.30	$20.30	$20.30
Purchase #5	$218.66	10.708%	$242.0741	$242.07	$242.05	$242.10
Purchase #6	$221.89	7.658%	$238.8823	$238.88	$238.90	$238.90
Purchase #7	$186.48	10.826%	$206.6683	$206.67	$206.65	$206.70
7 purchase totals =	$1,052.81		$1,139.4799	$1,139.48	$1,139.50	$1,139.60