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	$55.46	7.167%	$59.4348	$59.43	$59.45	$59.40
Purchase #2	$136.93	12.114%	$153.5177	$153.52	$153.50	$153.50
Purchase #3	$56.80	10.673%	$62.8623	$62.86	$62.85	$62.90
Purchase #4	$166.87	11.326%	$185.7697	$185.77	$185.75	$185.80
Purchase #5	$31.66	11.719%	$35.3702	$35.37	$35.35	$35.40
Purchase #6	$23.84	7.709%	$25.6778	$25.68	$25.70	$25.70
Purchase #7	$155.87	6.728%	$166.3569	$166.36	$166.35	$166.40
7 purchase totals =	$627.43		$688.9894	$688.99	$688.95	$689.10