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	$9.40	11.535%	$10.4843	$10.48	$10.50	$10.50
Purchase #2	$57.62	6.304%	$61.2524	$61.25	$61.25	$61.30
Purchase #3	$241.70	4.629%	$252.8883	$252.89	$252.90	$252.90
Purchase #4	$15.38	12.619%	$17.3208	$17.32	$17.30	$17.30
Purchase #5	$19.78	3.742%	$20.5202	$20.52	$20.50	$20.50
Purchase #6	$29.88	9.265%	$32.6484	$32.65	$32.65	$32.60
Purchase #7	$200.56	7.355%	$215.3112	$215.31	$215.30	$215.30
7 purchase totals =	$574.32		$610.4256	$610.42	$610.40	$610.40