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	$63.56	12.666%	$71.6105	$71.61	$71.60	$71.60
Purchase #2	$161.74	13.415%	$183.4374	$183.44	$183.45	$183.40
Purchase #3	$216.61	11.643%	$241.8299	$241.83	$241.85	$241.80
Purchase #4	$93.67	11.499%	$104.4411	$104.44	$104.45	$104.40
Purchase #5	$88.79	4.536%	$92.8175	$92.82	$92.80	$92.80
Purchase #6	$101.52	3.725%	$105.3016	$105.30	$105.30	$105.30
Purchase #7	$185.80	11.496%	$207.1596	$207.16	$207.15	$207.20
7 purchase totals =	$911.69		$1,006.5976	$1,006.60	$1,006.60	$1,006.50