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	$158.73	5.601%	$167.6205	$167.62	$167.60	$167.60
Purchase #2	$47.89	10.393%	$52.8672	$52.87	$52.85	$52.90
Purchase #3	$41.62	6.810%	$44.4543	$44.45	$44.45	$44.50
Purchase #4	$203.95	5.813%	$215.8056	$215.81	$215.80	$215.80
Purchase #5	$43.29	6.841%	$46.2515	$46.25	$46.25	$46.30
Purchase #6	$108.25	4.258%	$112.8593	$112.86	$112.85	$112.90
Purchase #7	$248.58	3.127%	$256.3531	$256.35	$256.35	$256.40
7 purchase totals =	$852.31		$896.2115	$896.21	$896.15	$896.40