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	$59.34	10.293%	$65.4479	$65.45	$65.45	$65.40
Purchase #2	$124.58	12.588%	$140.2621	$140.26	$140.25	$140.30
Purchase #3	$76.97	4.428%	$80.3782	$80.38	$80.40	$80.40
Purchase #4	$151.54	10.395%	$167.2926	$167.29	$167.30	$167.30
Purchase #5	$143.27	3.389%	$148.1254	$148.13	$148.15	$148.10
Purchase #6	$213.25	11.789%	$238.39	$238.39	$238.40	$238.40
Purchase #7	$126.45	4.476%	$132.1099	$132.11	$132.10	$132.10
7 purchase totals =	$895.40		$972.0061	$972.01	$972.05	$972.00