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	$25.99	11.661%	$29.0207	$29.02	$29.00	$29.00
Purchase #2	$181.99	4.711%	$190.5635	$190.56	$190.55	$190.60
Purchase #3	$134.43	13.355%	$152.3831	$152.38	$152.40	$152.40
Purchase #4	$183.50	13.803%	$208.8285	$208.83	$208.85	$208.80
Purchase #5	$136.56	10.187%	$150.4714	$150.47	$150.45	$150.50
Purchase #6	$242.31	12.290%	$272.0899	$272.09	$272.10	$272.10
Purchase #7	$42.98	7.775%	$46.3217	$46.32	$46.30	$46.30
7 purchase totals =	$947.76		$1,049.6788	$1,049.67	$1,049.65	$1,049.70