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	$140.60	12.570%	$158.2734	$158.27	$158.25	$158.30
Purchase #2	$230.62	4.272%	$240.4721	$240.47	$240.45	$240.50
Purchase #3	$41.34	6.240%	$43.9196	$43.92	$43.90	$43.90
Purchase #4	$239.66	10.772%	$265.4762	$265.48	$265.50	$265.50
Purchase #5	$140.91	11.797%	$157.5332	$157.53	$157.55	$157.50
Purchase #6	$35.53	5.748%	$37.5723	$37.57	$37.55	$37.60
Purchase #7	$168.38	7.167%	$180.4478	$180.45	$180.45	$180.40
7 purchase totals =	$997.04		$1,083.6946	$1,083.69	$1,083.65	$1,083.70