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	$111.74	10.298%	$123.247	$123.25	$123.25	$123.20
Purchase #2	$216.70	4.503%	$226.458	$226.46	$226.45	$226.50
Purchase #3	$174.54	5.757%	$184.5883	$184.59	$184.60	$184.60
Purchase #4	$189.75	4.803%	$198.8637	$198.86	$198.85	$198.90
Purchase #5	$29.66	10.774%	$32.8556	$32.86	$32.85	$32.90
Purchase #6	$196.97	5.380%	$207.567	$207.57	$207.55	$207.60
Purchase #7	$91.54	13.150%	$103.5775	$103.58	$103.60	$103.60
7 purchase totals =	$1,010.90		$1,077.1571	$1,077.17	$1,077.15	$1,077.30