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	$206.86	7.745%	$222.8813	$222.88	$222.90	$222.90
Purchase #2	$130.85	11.172%	$145.4686	$145.47	$145.45	$145.50
Purchase #3	$74.97	3.399%	$77.5182	$77.52	$77.50	$77.50
Purchase #4	$213.38	13.599%	$242.3975	$242.40	$242.40	$242.40
Purchase #5	$110.92	4.665%	$116.0944	$116.09	$116.10	$116.10
Purchase #6	$143.43	7.791%	$154.6046	$154.60	$154.60	$154.60
Purchase #7	$78.81	9.444%	$86.2528	$86.25	$86.25	$86.30
7 purchase totals =	$959.22		$1,045.2174	$1,045.21	$1,045.20	$1,045.30