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	$198.34	8.545%	$215.2882	$215.29	$215.30	$215.30
Purchase #2	$247.43	13.380%	$280.5361	$280.54	$280.55	$280.50
Purchase #3	$44.34	9.570%	$48.5833	$48.58	$48.60	$48.60
Purchase #4	$224.76	9.520%	$246.1572	$246.16	$246.15	$246.20
Purchase #5	$53.62	3.749%	$55.6302	$55.63	$55.65	$55.60
Purchase #6	$145.26	4.272%	$151.4655	$151.47	$151.45	$151.50
Purchase #7	$34.98	10.481%	$38.6463	$38.65	$38.65	$38.60
7 purchase totals =	$948.73		$1,036.3068	$1,036.32	$1,036.35	$1,036.30