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	$116.80	5.383%	$123.0873	$123.09	$123.10	$123.10
Purchase #2	$152.71	12.817%	$172.2828	$172.28	$172.30	$172.30
Purchase #3	$151.34	7.571%	$162.798	$162.80	$162.80	$162.80
Purchase #4	$5.25	3.760%	$5.4474	$5.45	$5.45	$5.40
Purchase #5	$246.30	5.462%	$259.7529	$259.75	$259.75	$259.80
Purchase #6	$196.26	13.422%	$222.602	$222.60	$222.60	$222.60
Purchase #7	$35.31	6.276%	$37.5261	$37.53	$37.55	$37.50
7 purchase totals =	$903.97		$983.4965	$983.50	$983.55	$983.50