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	$184.39	6.478%	$196.3348	$196.33	$196.35	$196.30
Purchase #2	$170.75	7.847%	$184.1488	$184.15	$184.15	$184.10
Purchase #3	$137.89	9.175%	$150.5414	$150.54	$150.55	$150.50
Purchase #4	$106.39	5.336%	$112.067	$112.07	$112.05	$112.10
Purchase #5	$111.63	7.250%	$119.7232	$119.72	$119.70	$119.70
Purchase #6	$99.45	5.203%	$104.6244	$104.62	$104.60	$104.60
Purchase #7	$240.35	13.506%	$272.8117	$272.81	$272.80	$272.80
7 purchase totals =	$1,050.85		$1,140.2513	$1,140.24	$1,140.20	$1,140.10