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	$43.31	9.257%	$47.3192	$47.32	$47.30	$47.30
Purchase #2	$119.83	3.559%	$124.0947	$124.09	$124.10	$124.10
Purchase #3	$6.97	8.595%	$7.5691	$7.57	$7.55	$7.60
Purchase #4	$31.83	5.650%	$33.6284	$33.63	$33.65	$33.60
Purchase #5	$19.86	3.131%	$20.4818	$20.48	$20.50	$20.50
Purchase #6	$98.80	8.370%	$107.0696	$107.07	$107.05	$107.10
Purchase #7	$145.90	8.795%	$158.7319	$158.73	$158.75	$158.70
7 purchase totals =	$466.50		$498.8947	$498.89	$498.90	$498.90