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	$88.59	3.356%	$91.5631	$91.56	$91.55	$91.60
Purchase #2	$191.54	5.329%	$201.7472	$201.75	$201.75	$201.70
Purchase #3	$81.32	11.241%	$90.4612	$90.46	$90.45	$90.50
Purchase #4	$151.65	13.465%	$172.0697	$172.07	$172.05	$172.10
Purchase #5	$14.28	4.162%	$14.8743	$14.87	$14.85	$14.90
Purchase #6	$239.38	11.405%	$266.6813	$266.68	$266.70	$266.70
Purchase #7	$192.40	13.533%	$218.4375	$218.44	$218.45	$218.40
7 purchase totals =	$959.16		$1,055.8343	$1,055.83	$1,055.80	$1,055.90