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	$114.40	4.257%	$119.27	$119.27	$119.25	$119.30
Purchase #2	$151.90	13.252%	$172.0298	$172.03	$172.05	$172.00
Purchase #3	$40.88	8.605%	$44.3977	$44.40	$44.40	$44.40
Purchase #4	$80.34	4.439%	$83.9063	$83.91	$83.90	$83.90
Purchase #5	$157.88	8.576%	$171.4198	$171.42	$171.40	$171.40
Purchase #6	$225.38	8.411%	$244.3367	$244.34	$244.35	$244.30
Purchase #7	$127.64	10.181%	$140.635	$140.64	$140.65	$140.60
7 purchase totals =	$898.42		$975.9953	$976.01	$976.00	$975.90