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	$105.30	8.719%	$114.4811	$114.48	$114.50	$114.50
Purchase #2	$196.55	6.853%	$210.0196	$210.02	$210.00	$210.00
Purchase #3	$108.98	13.139%	$123.2989	$123.30	$123.30	$123.30
Purchase #4	$145.48	6.775%	$155.3363	$155.34	$155.35	$155.30
Purchase #5	$32.68	5.256%	$34.3977	$34.40	$34.40	$34.40
Purchase #6	$28.50	10.621%	$31.527	$31.53	$31.55	$31.50
Purchase #7	$39.63	13.492%	$44.9769	$44.98	$45.00	$45.00
7 purchase totals =	$657.12		$714.0375	$714.05	$714.10	$714.00