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	$39.82	9.174%	$43.4731	$43.47	$43.45	$43.50
Purchase #2	$25.44	12.394%	$28.593	$28.59	$28.60	$28.60
Purchase #3	$73.98	8.829%	$80.5117	$80.51	$80.50	$80.50
Purchase #4	$237.64	13.539%	$269.8141	$269.81	$269.80	$269.80
Purchase #5	$158.61	5.462%	$167.2733	$167.27	$167.25	$167.30
Purchase #6	$109.52	6.726%	$116.8863	$116.89	$116.90	$116.90
Purchase #7	$238.60	8.822%	$259.6493	$259.65	$259.65	$259.60
7 purchase totals =	$883.61		$966.2008	$966.19	$966.15	$966.20