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	$192.82	13.860%	$219.5449	$219.54	$219.55	$219.50
Purchase #2	$153.58	9.458%	$168.1056	$168.11	$168.10	$168.10
Purchase #3	$6.31	13.150%	$7.1398	$7.14	$7.15	$7.10
Purchase #4	$199.87	13.831%	$227.514	$227.51	$227.50	$227.50
Purchase #5	$40.76	3.284%	$42.0986	$42.10	$42.10	$42.10
Purchase #6	$173.85	6.750%	$185.5849	$185.58	$185.60	$185.60
Purchase #7	$203.35	10.509%	$224.7201	$224.72	$224.70	$224.70
7 purchase totals =	$970.54		$1,074.7079	$1,074.70	$1,074.70	$1,074.60