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	$238.50	8.422%	$258.5865	$258.59	$258.60	$258.60
Purchase #2	$174.33	6.387%	$185.4645	$185.46	$185.45	$185.50
Purchase #3	$61.38	10.828%	$68.0262	$68.03	$68.05	$68.00
Purchase #4	$192.78	4.712%	$201.8638	$201.86	$201.85	$201.90
Purchase #5	$188.92	12.787%	$213.0772	$213.08	$213.10	$213.10
Purchase #6	$69.28	3.134%	$71.4512	$71.45	$71.45	$71.50
Purchase #7	$53.91	13.322%	$61.0919	$61.09	$61.10	$61.10
7 purchase totals =	$979.10		$1,059.5613	$1,059.56	$1,059.60	$1,059.70