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	$137.70	10.225%	$151.7798	$151.78	$151.80	$151.80
Purchase #2	$18.25	8.661%	$19.8306	$19.83	$19.85	$19.80
Purchase #3	$111.69	10.515%	$123.4342	$123.43	$123.45	$123.40
Purchase #4	$47.50	8.473%	$51.5247	$51.52	$51.50	$51.50
Purchase #5	$235.36	7.135%	$252.1529	$252.15	$252.15	$252.20
Purchase #6	$161.53	13.497%	$183.3317	$183.33	$183.35	$183.30
Purchase #7	$242.29	7.236%	$259.8221	$259.82	$259.80	$259.80
7 purchase totals =	$954.32		$1,041.8760	$1,041.86	$1,041.90	$1,041.80