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	$65.45	11.506%	$72.9807	$72.98	$73.00	$73.00
Purchase #2	$10.79	7.298%	$11.5775	$11.58	$11.60	$11.60
Purchase #3	$28.88	9.535%	$31.6337	$31.63	$31.65	$31.60
Purchase #4	$193.42	13.543%	$219.6149	$219.61	$219.60	$219.60
Purchase #5	$216.86	4.154%	$225.8684	$225.87	$225.85	$225.90
Purchase #6	$66.26	6.287%	$70.4258	$70.43	$70.45	$70.40
Purchase #7	$246.31	13.839%	$280.3968	$280.40	$280.40	$280.40
7 purchase totals =	$827.97		$912.4978	$912.50	$912.55	$912.50