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	$115.61	10.446%	$127.6866	$127.69	$127.70	$127.70
Purchase #2	$239.56	11.452%	$266.9944	$266.99	$267.00	$267.00
Purchase #3	$114.61	6.783%	$122.384	$122.38	$122.40	$122.40
Purchase #4	$121.92	4.611%	$127.5417	$127.54	$127.55	$127.50
Purchase #5	$224.60	10.535%	$248.2616	$248.26	$248.25	$248.30
Purchase #6	$99.61	11.512%	$111.0771	$111.08	$111.10	$111.10
Purchase #7	$6.66	4.744%	$6.976	$6.98	$7.00	$7.00
7 purchase totals =	$922.57		$1,010.9214	$1,010.92	$1,011.00	$1,011.00