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	$94.32	6.728%	$100.6658	$100.67	$100.65	$100.70
Purchase #2	$216.50	7.838%	$233.4693	$233.47	$233.45	$233.50
Purchase #3	$34.55	3.289%	$35.6863	$35.69	$35.70	$35.70
Purchase #4	$213.45	4.683%	$223.4459	$223.45	$223.45	$223.40
Purchase #5	$226.71	12.774%	$255.6699	$255.67	$255.65	$255.70
Purchase #6	$230.72	3.149%	$237.9854	$237.99	$238.00	$238.00
Purchase #7	$28.33	3.701%	$29.3785	$29.38	$29.40	$29.40
7 purchase totals =	$1,044.58		$1,116.3011	$1,116.32	$1,116.30	$1,116.40