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	$219.67	8.577%	$238.5111	$238.51	$238.50	$238.50
Purchase #2	$71.62	13.718%	$81.4448	$81.44	$81.45	$81.40
Purchase #3	$76.67	6.330%	$81.5232	$81.52	$81.50	$81.50
Purchase #4	$59.31	5.617%	$62.6414	$62.64	$62.65	$62.60
Purchase #5	$38.82	4.104%	$40.4132	$40.41	$40.40	$40.40
Purchase #6	$195.73	10.714%	$216.7005	$216.70	$216.70	$216.70
Purchase #7	$212.32	8.136%	$229.5944	$229.59	$229.60	$229.60
7 purchase totals =	$874.14		$950.8286	$950.81	$950.80	$950.70