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	$240.60	13.859%	$273.9448	$273.94	$273.95	$273.90
Purchase #2	$45.95	5.114%	$48.2999	$48.30	$48.30	$48.30
Purchase #3	$181.70	5.112%	$190.9885	$190.99	$191.00	$191.00
Purchase #4	$54.70	4.340%	$57.074	$57.07	$57.05	$57.10
Purchase #5	$64.37	3.784%	$66.8058	$66.81	$66.80	$66.80
Purchase #6	$130.56	10.559%	$144.3458	$144.35	$144.35	$144.30
Purchase #7	$211.68	9.187%	$231.127	$231.13	$231.15	$231.10
7 purchase totals =	$929.56		$1,012.5858	$1,012.59	$1,012.60	$1,012.50