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	$33.95	10.546%	$37.5304	$37.53	$37.55	$37.50
Purchase #2	$226.72	12.372%	$254.7698	$254.77	$254.75	$254.80
Purchase #3	$222.75	7.205%	$238.7991	$238.80	$238.80	$238.80
Purchase #4	$107.43	10.147%	$118.3309	$118.33	$118.35	$118.30
Purchase #5	$94.53	6.780%	$100.9391	$100.94	$100.95	$100.90
Purchase #6	$142.79	3.786%	$148.196	$148.20	$148.20	$148.20
Purchase #7	$103.92	8.587%	$112.8436	$112.84	$112.85	$112.80
7 purchase totals =	$932.09		$1,011.4089	$1,011.41	$1,011.45	$1,011.30