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	$56.28	9.356%	$61.5456	$61.55	$61.55	$61.50
Purchase #2	$229.72	9.510%	$251.5664	$251.57	$251.55	$251.60
Purchase #3	$103.67	5.838%	$109.7223	$109.72	$109.70	$109.70
Purchase #4	$121.77	12.736%	$137.2786	$137.28	$137.30	$137.30
Purchase #5	$12.82	12.820%	$14.4635	$14.46	$14.45	$14.50
Purchase #6	$151.61	4.394%	$158.2717	$158.27	$158.25	$158.30
Purchase #7	$123.48	8.805%	$134.3524	$134.35	$134.35	$134.40
7 purchase totals =	$799.35		$867.2005	$867.20	$867.15	$867.30