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	$86.77	4.683%	$90.8334	$90.83	$90.85	$90.80
Purchase #2	$52.25	5.395%	$55.0689	$55.07	$55.05	$55.10
Purchase #3	$88.93	10.429%	$98.2045	$98.20	$98.20	$98.20
Purchase #4	$225.64	5.526%	$238.1089	$238.11	$238.10	$238.10
Purchase #5	$66.83	8.617%	$72.5887	$72.59	$72.60	$72.60
Purchase #6	$108.35	10.521%	$119.7495	$119.75	$119.75	$119.70
Purchase #7	$60.44	6.283%	$64.2374	$64.24	$64.25	$64.20
7 purchase totals =	$689.21		$738.7913	$738.79	$738.80	$738.70