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	$237.78	10.548%	$262.861	$262.86	$262.85	$262.90
Purchase #2	$177.34	4.829%	$185.9037	$185.90	$185.90	$185.90
Purchase #3	$14.72	7.154%	$15.7731	$15.77	$15.75	$15.80
Purchase #4	$180.59	10.147%	$198.9145	$198.91	$198.90	$198.90
Purchase #5	$198.67	12.558%	$223.619	$223.62	$223.60	$223.60
Purchase #6	$212.96	13.656%	$242.0418	$242.04	$242.05	$242.00
Purchase #7	$111.86	7.213%	$119.9285	$119.93	$119.95	$119.90
7 purchase totals =	$1,133.92		$1,249.0416	$1,249.03	$1,249.00	$1,249.00