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	$158.54	11.458%	$176.7055	$176.71	$176.70	$176.70
Purchase #2	$222.86	8.259%	$241.266	$241.27	$241.25	$241.30
Purchase #3	$169.38	4.134%	$176.3822	$176.38	$176.40	$176.40
Purchase #4	$72.74	10.169%	$80.1369	$80.14	$80.15	$80.10
Purchase #5	$182.96	9.776%	$200.8462	$200.85	$200.85	$200.80
Purchase #6	$108.71	6.349%	$115.612	$115.61	$115.60	$115.60
Purchase #7	$54.72	10.752%	$60.6035	$60.60	$60.60	$60.60
7 purchase totals =	$969.91		$1,051.5523	$1,051.56	$1,051.55	$1,051.50