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	$120.45	8.871%	$131.1351	$131.14	$131.15	$131.10
Purchase #2	$102.52	8.533%	$111.268	$111.27	$111.25	$111.30
Purchase #3	$35.58	6.613%	$37.9329	$37.93	$37.95	$37.90
Purchase #4	$31.90	13.748%	$36.2856	$36.29	$36.30	$36.30
Purchase #5	$133.96	3.682%	$138.8924	$138.89	$138.90	$138.90
Purchase #6	$138.96	4.775%	$145.5953	$145.60	$145.60	$145.60
Purchase #7	$13.53	9.265%	$14.7836	$14.78	$14.80	$14.80
7 purchase totals =	$576.90		$615.8929	$615.90	$615.95	$615.90