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	$13.43	10.630%	$14.8576	$14.86	$14.85	$14.90
Purchase #2	$238.39	10.336%	$263.03	$263.03	$263.05	$263.00
Purchase #3	$44.51	12.662%	$50.1459	$50.15	$50.15	$50.10
Purchase #4	$43.46	5.708%	$45.9407	$45.94	$45.95	$45.90
Purchase #5	$61.39	11.526%	$68.4658	$68.47	$68.45	$68.50
Purchase #6	$94.92	10.838%	$105.2074	$105.21	$105.20	$105.20
Purchase #7	$122.59	6.357%	$130.383	$130.38	$130.40	$130.40
7 purchase totals =	$618.69		$678.0304	$678.04	$678.05	$678.00