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	$107.68	3.405%	$111.3465	$111.35	$111.35	$111.30
Purchase #2	$88.79	10.390%	$98.0153	$98.02	$98.00	$98.00
Purchase #3	$240.67	6.624%	$256.612	$256.61	$256.60	$256.60
Purchase #4	$89.72	4.540%	$93.7933	$93.79	$93.80	$93.80
Purchase #5	$85.89	12.705%	$96.8023	$96.80	$96.80	$96.80
Purchase #6	$10.81	12.829%	$12.1968	$12.20	$12.20	$12.20
Purchase #7	$203.37	9.342%	$222.3688	$222.37	$222.35	$222.40
7 purchase totals =	$826.93		$891.1350	$891.14	$891.10	$891.10