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	$115.78	11.367%	$128.9407	$128.94	$128.95	$128.90
Purchase #2	$247.28	13.480%	$280.6133	$280.61	$280.60	$280.60
Purchase #3	$225.62	5.465%	$237.9501	$237.95	$237.95	$238.00
Purchase #4	$244.62	7.538%	$263.0595	$263.06	$263.05	$263.10
Purchase #5	$163.27	7.150%	$174.9438	$174.94	$174.95	$174.90
Purchase #6	$71.52	12.493%	$80.455	$80.46	$80.45	$80.50
Purchase #7	$60.85	7.721%	$65.5482	$65.55	$65.55	$65.50
7 purchase totals =	$1,128.94		$1,231.5106	$1,231.51	$1,231.50	$1,231.50