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	$213.33	12.289%	$239.5461	$239.55	$239.55	$239.50
Purchase #2	$92.62	11.741%	$103.4945	$103.49	$103.50	$103.50
Purchase #3	$139.82	7.311%	$150.0422	$150.04	$150.05	$150.00
Purchase #4	$128.51	8.227%	$139.0825	$139.08	$139.10	$139.10
Purchase #5	$131.95	8.247%	$142.8319	$142.83	$142.85	$142.80
Purchase #6	$224.74	8.510%	$243.8654	$243.87	$243.85	$243.90
Purchase #7	$41.50	5.256%	$43.6812	$43.68	$43.70	$43.70
7 purchase totals =	$972.47		$1,062.5438	$1,062.54	$1,062.60	$1,062.50