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	$56.46	10.488%	$62.3815	$62.38	$62.40	$62.40
Purchase #2	$131.42	12.326%	$147.6188	$147.62	$147.60	$147.60
Purchase #3	$97.46	7.182%	$104.4596	$104.46	$104.45	$104.50
Purchase #4	$196.62	6.741%	$209.8742	$209.87	$209.85	$209.90
Purchase #5	$131.81	6.193%	$139.973	$139.97	$139.95	$140.00
Purchase #6	$248.82	10.344%	$274.5579	$274.56	$274.55	$274.60
Purchase #7	$40.65	5.823%	$43.017	$43.02	$43.00	$43.00
7 purchase totals =	$903.24		$981.8820	$981.88	$981.80	$982.00