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	$224.57	5.702%	$237.375	$237.38	$237.40	$237.40
Purchase #2	$128.90	12.533%	$145.055	$145.06	$145.05	$145.10
Purchase #3	$138.31	11.683%	$154.4688	$154.47	$154.45	$154.50
Purchase #4	$187.25	3.633%	$194.0528	$194.05	$194.05	$194.10
Purchase #5	$13.51	4.693%	$14.144	$14.14	$14.15	$14.10
Purchase #6	$140.54	12.690%	$158.3745	$158.37	$158.35	$158.40
Purchase #7	$168.33	5.843%	$178.1655	$178.17	$178.15	$178.20
7 purchase totals =	$1,001.41		$1,081.6356	$1,081.64	$1,081.60	$1,081.80