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	$158.44	11.561%	$176.7572	$176.76	$176.75	$176.80
Purchase #2	$225.78	8.345%	$244.6213	$244.62	$244.60	$244.60
Purchase #3	$204.40	8.855%	$222.4996	$222.50	$222.50	$222.50
Purchase #4	$190.25	8.182%	$205.8163	$205.82	$205.80	$205.80
Purchase #5	$41.28	5.387%	$43.5038	$43.50	$43.50	$43.50
Purchase #6	$100.53	11.547%	$112.1382	$112.14	$112.15	$112.10
Purchase #7	$30.27	5.112%	$31.8174	$31.82	$31.80	$31.80
7 purchase totals =	$950.95		$1,037.1538	$1,037.16	$1,037.10	$1,037.10