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	$192.40	4.427%	$200.9175	$200.92	$200.90	$200.90
Purchase #2	$107.35	4.809%	$112.5125	$112.51	$112.50	$112.50
Purchase #3	$39.47	9.273%	$43.1301	$43.13	$43.15	$43.10
Purchase #4	$224.60	6.105%	$238.3118	$238.31	$238.30	$238.30
Purchase #5	$231.63	10.173%	$255.1937	$255.19	$255.20	$255.20
Purchase #6	$228.56	3.789%	$237.2201	$237.22	$237.20	$237.20
Purchase #7	$216.91	3.203%	$223.8576	$223.86	$223.85	$223.90
7 purchase totals =	$1,240.92		$1,311.1433	$1,311.14	$1,311.10	$1,311.10