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	$43.52	9.403%	$47.6122	$47.61	$47.60	$47.60
Purchase #2	$205.56	4.642%	$215.1021	$215.10	$215.10	$215.10
Purchase #3	$11.55	12.716%	$13.0187	$13.02	$13.00	$13.00
Purchase #4	$88.88	9.218%	$97.073	$97.07	$97.05	$97.10
Purchase #5	$92.28	8.652%	$100.2641	$100.26	$100.25	$100.30
Purchase #6	$159.52	7.751%	$171.8844	$171.88	$171.90	$171.90
Purchase #7	$16.40	10.113%	$18.0585	$18.06	$18.05	$18.10
7 purchase totals =	$617.71		$663.0130	$663.00	$662.95	$663.10