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	$36.47	10.262%	$40.2126	$40.21	$40.20	$40.20
Purchase #2	$130.53	5.517%	$137.7313	$137.73	$137.75	$137.70
Purchase #3	$105.70	5.331%	$111.3349	$111.33	$111.35	$111.30
Purchase #4	$200.77	13.456%	$227.7856	$227.79	$227.80	$227.80
Purchase #5	$120.64	11.474%	$134.4822	$134.48	$134.50	$134.50
Purchase #6	$191.51	11.240%	$213.0357	$213.04	$213.05	$213.00
Purchase #7	$42.53	10.797%	$47.122	$47.12	$47.10	$47.10
7 purchase totals =	$828.15		$911.7043	$911.70	$911.75	$911.60