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	$43.44	3.246%	$44.8501	$44.85	$44.85	$44.90
Purchase #2	$109.38	7.314%	$117.3801	$117.38	$117.40	$117.40
Purchase #3	$111.88	5.868%	$118.4451	$118.45	$118.45	$118.40
Purchase #4	$76.34	7.392%	$81.9831	$81.98	$82.00	$82.00
Purchase #5	$74.78	5.232%	$78.6925	$78.69	$78.70	$78.70
Purchase #6	$164.70	4.857%	$172.6995	$172.70	$172.70	$172.70
Purchase #7	$170.82	9.141%	$186.4347	$186.43	$186.45	$186.40
7 purchase totals =	$751.34		$800.4851	$800.48	$800.55	$800.50