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	$127.31	4.276%	$132.7538	$132.75	$132.75	$132.80
Purchase #2	$151.31	5.849%	$160.1601	$160.16	$160.15	$160.20
Purchase #3	$209.31	3.400%	$216.4265	$216.43	$216.45	$216.40
Purchase #4	$104.72	9.647%	$114.8223	$114.82	$114.80	$114.80
Purchase #5	$92.26	6.212%	$97.9912	$97.99	$98.00	$98.00
Purchase #6	$111.25	13.667%	$126.4545	$126.45	$126.45	$126.50
Purchase #7	$109.56	12.795%	$123.5782	$123.58	$123.60	$123.60
7 purchase totals =	$905.72		$972.1866	$972.18	$972.20	$972.30