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	$171.39	5.547%	$180.897	$180.90	$180.90	$180.90
Purchase #2	$66.46	7.334%	$71.3342	$71.33	$71.35	$71.30
Purchase #3	$81.31	3.641%	$84.2705	$84.27	$84.25	$84.30
Purchase #4	$95.72	4.854%	$100.3662	$100.37	$100.35	$100.40
Purchase #5	$178.66	8.236%	$193.3744	$193.37	$193.35	$193.40
Purchase #6	$175.38	10.656%	$194.0685	$194.07	$194.05	$194.10
Purchase #7	$229.30	3.616%	$237.5915	$237.59	$237.60	$237.60
7 purchase totals =	$998.22		$1,061.9023	$1,061.90	$1,061.85	$1,062.00