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	$221.51	12.339%	$248.8421	$248.84	$248.85	$248.80
Purchase #2	$105.26	4.329%	$109.8167	$109.82	$109.80	$109.80
Purchase #3	$69.48	13.434%	$78.8139	$78.81	$78.80	$78.80
Purchase #4	$49.30	7.553%	$53.0236	$53.02	$53.00	$53.00
Purchase #5	$61.89	7.706%	$66.6592	$66.66	$66.65	$66.70
Purchase #6	$195.37	6.297%	$207.6724	$207.67	$207.65	$207.70
Purchase #7	$231.34	10.228%	$255.0015	$255.00	$255.00	$255.00
7 purchase totals =	$934.15		$1,019.8294	$1,019.82	$1,019.75	$1,019.80