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	$207.67	4.716%	$217.4637	$217.46	$217.45	$217.50
Purchase #2	$73.85	11.626%	$82.4358	$82.44	$82.45	$82.40
Purchase #3	$182.55	11.524%	$203.5871	$203.59	$203.60	$203.60
Purchase #4	$72.90	13.679%	$82.872	$82.87	$82.85	$82.90
Purchase #5	$193.87	11.382%	$215.9363	$215.94	$215.95	$215.90
Purchase #6	$138.62	8.439%	$150.3181	$150.32	$150.30	$150.30
Purchase #7	$90.89	13.498%	$103.1583	$103.16	$103.15	$103.20
7 purchase totals =	$960.35		$1,055.7713	$1,055.78	$1,055.75	$1,055.80