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	$126.36	10.615%	$139.7731	$139.77	$139.75	$139.80
Purchase #2	$17.71	9.619%	$19.4135	$19.41	$19.40	$19.40
Purchase #3	$34.38	7.832%	$37.0726	$37.07	$37.05	$37.10
Purchase #4	$142.79	6.173%	$151.6044	$151.60	$151.60	$151.60
Purchase #5	$44.77	5.730%	$47.3353	$47.34	$47.35	$47.30
Purchase #6	$198.86	8.848%	$216.4551	$216.46	$216.45	$216.50
Purchase #7	$151.99	13.773%	$172.9236	$172.92	$172.90	$172.90
7 purchase totals =	$716.86		$784.5776	$784.57	$784.50	$784.60