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	$130.56	5.130%	$137.2577	$137.26	$137.25	$137.30
Purchase #2	$82.58	4.685%	$86.4489	$86.45	$86.45	$86.40
Purchase #3	$35.97	10.779%	$39.8472	$39.85	$39.85	$39.80
Purchase #4	$55.97	8.159%	$60.5366	$60.54	$60.55	$60.50
Purchase #5	$182.29	13.752%	$207.3585	$207.36	$207.35	$207.40
Purchase #6	$27.94	12.497%	$31.4317	$31.43	$31.45	$31.40
Purchase #7	$57.45	4.314%	$59.9284	$59.93	$59.95	$59.90
7 purchase totals =	$572.76		$622.8090	$622.82	$622.85	$622.70