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	$170.79	3.301%	$176.4278	$176.43	$176.45	$176.40
Purchase #2	$183.60	11.804%	$205.2721	$205.27	$205.25	$205.30
Purchase #3	$179.71	11.300%	$200.0172	$200.02	$200.00	$200.00
Purchase #4	$134.68	5.848%	$142.5561	$142.56	$142.55	$142.60
Purchase #5	$6.97	11.675%	$7.7837	$7.78	$7.80	$7.80
Purchase #6	$201.53	5.670%	$212.9568	$212.96	$212.95	$213.00
Purchase #7	$74.44	5.175%	$78.2923	$78.29	$78.30	$78.30
7 purchase totals =	$951.72		$1,023.3060	$1,023.31	$1,023.30	$1,023.40