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	$144.97	3.123%	$149.4974	$149.50	$149.50	$149.50
Purchase #2	$52.81	12.725%	$59.5301	$59.53	$59.55	$59.50
Purchase #3	$50.74	6.292%	$53.9326	$53.93	$53.95	$53.90
Purchase #4	$189.61	7.379%	$203.6013	$203.60	$203.60	$203.60
Purchase #5	$242.66	4.665%	$253.9801	$253.98	$254.00	$254.00
Purchase #6	$130.48	10.837%	$144.6201	$144.62	$144.60	$144.60
Purchase #7	$192.82	10.429%	$212.9292	$212.93	$212.95	$212.90
7 purchase totals =	$1,004.09		$1,078.0908	$1,078.09	$1,078.15	$1,078.00