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	$164.45	9.261%	$179.6797	$179.68	$179.70	$179.70
Purchase #2	$212.83	13.530%	$241.6259	$241.63	$241.65	$241.60
Purchase #3	$103.52	13.383%	$117.3741	$117.37	$117.35	$117.40
Purchase #4	$177.32	7.865%	$191.2662	$191.27	$191.25	$191.30
Purchase #5	$52.74	13.131%	$59.6653	$59.67	$59.65	$59.70
Purchase #6	$196.44	12.189%	$220.3841	$220.38	$220.40	$220.40
Purchase #7	$94.92	5.589%	$100.2251	$100.23	$100.25	$100.20
7 purchase totals =	$1,002.22		$1,110.2204	$1,110.23	$1,110.25	$1,110.30