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	$232.91	9.814%	$255.7678	$255.77	$255.75	$255.80
Purchase #2	$44.91	3.307%	$46.3952	$46.40	$46.40	$46.40
Purchase #3	$173.83	3.203%	$179.3978	$179.40	$179.40	$179.40
Purchase #4	$116.68	5.638%	$123.2584	$123.26	$123.25	$123.30
Purchase #5	$89.96	4.811%	$94.288	$94.29	$94.30	$94.30
Purchase #6	$51.41	10.528%	$56.8224	$56.82	$56.80	$56.80
Purchase #7	$248.69	3.694%	$257.8766	$257.88	$257.90	$257.90
7 purchase totals =	$958.39		$1,013.8062	$1,013.82	$1,013.80	$1,013.90