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	$93.71	8.335%	$101.5207	$101.52	$101.50	$101.50
Purchase #2	$78.96	3.182%	$81.4725	$81.47	$81.45	$81.50
Purchase #3	$164.63	13.250%	$186.4435	$186.44	$186.45	$186.40
Purchase #4	$63.53	10.218%	$70.0215	$70.02	$70.00	$70.00
Purchase #5	$37.72	3.642%	$39.0938	$39.09	$39.10	$39.10
Purchase #6	$78.52	12.247%	$88.1363	$88.14	$88.15	$88.10
Purchase #7	$82.95	7.467%	$89.1439	$89.14	$89.15	$89.10
7 purchase totals =	$600.02		$655.8322	$655.82	$655.80	$655.70