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	$59.77	9.814%	$65.6358	$65.64	$65.65	$65.60
Purchase #2	$89.45	4.848%	$93.7865	$93.79	$93.80	$93.80
Purchase #3	$37.47	8.322%	$40.5883	$40.59	$40.60	$40.60
Purchase #4	$162.29	6.513%	$172.8599	$172.86	$172.85	$172.90
Purchase #5	$116.82	6.874%	$124.8502	$124.85	$124.85	$124.90
Purchase #6	$40.80	5.418%	$43.0105	$43.01	$43.00	$43.00
Purchase #7	$72.43	8.636%	$78.6851	$78.69	$78.70	$78.70
7 purchase totals =	$579.03		$619.4163	$619.43	$619.45	$619.50