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	$140.67	10.405%	$155.3067	$155.31	$155.30	$155.30
Purchase #2	$239.77	13.412%	$271.928	$271.93	$271.95	$271.90
Purchase #3	$164.86	10.132%	$181.5636	$181.56	$181.55	$181.60
Purchase #4	$146.68	12.176%	$164.5398	$164.54	$164.55	$164.50
Purchase #5	$151.56	10.752%	$167.8557	$167.86	$167.85	$167.90
Purchase #6	$184.73	8.557%	$200.5373	$200.54	$200.55	$200.50
Purchase #7	$128.75	8.438%	$139.6139	$139.61	$139.60	$139.60
7 purchase totals =	$1,157.02		$1,281.3450	$1,281.35	$1,281.35	$1,281.30