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	$151.59	8.498%	$164.4721	$164.47	$164.45	$164.50
Purchase #2	$61.51	7.767%	$66.2875	$66.29	$66.30	$66.30
Purchase #3	$134.74	9.255%	$147.2102	$147.21	$147.20	$147.20
Purchase #4	$73.71	11.781%	$82.3938	$82.39	$82.40	$82.40
Purchase #5	$133.55	3.291%	$137.9451	$137.95	$137.95	$137.90
Purchase #6	$241.64	5.584%	$255.1332	$255.13	$255.15	$255.10
Purchase #7	$203.71	3.538%	$210.9173	$210.92	$210.90	$210.90
7 purchase totals =	$1,000.45		$1,064.3592	$1,064.36	$1,064.35	$1,064.30