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	$117.40	5.171%	$123.4708	$123.47	$123.45	$123.50
Purchase #2	$131.76	4.355%	$137.4981	$137.50	$137.50	$137.50
Purchase #3	$196.89	5.438%	$207.5969	$207.60	$207.60	$207.60
Purchase #4	$93.96	9.714%	$103.0873	$103.09	$103.10	$103.10
Purchase #5	$33.86	11.473%	$37.7448	$37.74	$37.75	$37.70
Purchase #6	$91.27	3.555%	$94.5146	$94.51	$94.50	$94.50
Purchase #7	$249.28	9.151%	$272.0916	$272.09	$272.10	$272.10
7 purchase totals =	$914.42		$976.0041	$976.00	$976.00	$976.00