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	$124.37	13.791%	$141.5219	$141.52	$141.50	$141.50
Purchase #2	$172.45	10.266%	$190.1537	$190.15	$190.15	$190.20
Purchase #3	$176.91	13.500%	$200.7929	$200.79	$200.80	$200.80
Purchase #4	$213.30	6.474%	$227.109	$227.11	$227.10	$227.10
Purchase #5	$51.87	8.856%	$56.4636	$56.46	$56.45	$56.50
Purchase #6	$211.47	9.330%	$231.2002	$231.20	$231.20	$231.20
Purchase #7	$60.53	10.521%	$66.8984	$66.90	$66.90	$66.90
7 purchase totals =	$1,010.90		$1,114.1397	$1,114.13	$1,114.10	$1,114.20