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	$118.66	4.138%	$123.5702	$123.57	$123.55	$123.60
Purchase #2	$19.42	9.143%	$21.1956	$21.20	$21.20	$21.20
Purchase #3	$79.52	5.114%	$83.5867	$83.59	$83.60	$83.60
Purchase #4	$232.72	11.471%	$259.4153	$259.42	$259.40	$259.40
Purchase #5	$117.70	12.817%	$132.7856	$132.79	$132.80	$132.80
Purchase #6	$248.40	12.851%	$280.3219	$280.32	$280.30	$280.30
Purchase #7	$229.35	3.280%	$236.8727	$236.87	$236.85	$236.90
7 purchase totals =	$1,045.77		$1,137.7480	$1,137.76	$1,137.70	$1,137.80