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	$103.25	8.237%	$111.7547	$111.75	$111.75	$111.80
Purchase #2	$177.59	7.190%	$190.3587	$190.36	$190.35	$190.40
Purchase #3	$71.37	12.271%	$80.1278	$80.13	$80.15	$80.10
Purchase #4	$245.37	12.800%	$276.7774	$276.78	$276.80	$276.80
Purchase #5	$146.72	13.495%	$166.5199	$166.52	$166.50	$166.50
Purchase #6	$160.80	6.423%	$171.1282	$171.13	$171.15	$171.10
Purchase #7	$175.68	3.758%	$182.2821	$182.28	$182.30	$182.30
7 purchase totals =	$1,080.78		$1,178.9488	$1,178.95	$1,179.00	$1,179.00