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	$143.54	10.468%	$158.5658	$158.57	$158.55	$158.60
Purchase #2	$217.76	9.158%	$237.7025	$237.70	$237.70	$237.70
Purchase #3	$65.82	10.217%	$72.5448	$72.54	$72.55	$72.50
Purchase #4	$11.85	7.114%	$12.693	$12.69	$12.70	$12.70
Purchase #5	$42.26	3.364%	$43.6816	$43.68	$43.70	$43.70
Purchase #6	$84.59	13.803%	$96.266	$96.27	$96.25	$96.30
Purchase #7	$119.90	10.387%	$132.354	$132.35	$132.35	$132.40
7 purchase totals =	$685.72		$753.8077	$753.80	$753.80	$753.90