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	$58.36	5.439%	$61.5342	$61.53	$61.55	$61.50
Purchase #2	$77.94	3.358%	$80.5572	$80.56	$80.55	$80.60
Purchase #3	$40.59	8.804%	$44.1635	$44.16	$44.15	$44.20
Purchase #4	$250.82	11.637%	$280.0079	$280.01	$280.00	$280.00
Purchase #5	$103.52	7.647%	$111.4362	$111.44	$111.45	$111.40
Purchase #6	$233.32	5.142%	$245.3173	$245.32	$245.30	$245.30
Purchase #7	$137.70	6.264%	$146.3255	$146.33	$146.35	$146.30
7 purchase totals =	$902.25		$969.3418	$969.35	$969.35	$969.30