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	$37.61	13.850%	$42.819	$42.82	$42.80	$42.80
Purchase #2	$47.68	13.503%	$54.1182	$54.12	$54.10	$54.10
Purchase #3	$77.54	3.614%	$80.3423	$80.34	$80.35	$80.30
Purchase #4	$213.42	10.619%	$236.0831	$236.08	$236.10	$236.10
Purchase #5	$140.61	7.620%	$151.3245	$151.32	$151.30	$151.30
Purchase #6	$6.48	12.229%	$7.2724	$7.27	$7.25	$7.30
Purchase #7	$94.59	9.503%	$103.5789	$103.58	$103.60	$103.60
7 purchase totals =	$617.93		$675.5384	$675.53	$675.50	$675.50