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	$15.75	5.503%	$16.6167	$16.62	$16.60	$16.60
Purchase #2	$78.36	5.839%	$82.9354	$82.94	$82.95	$82.90
Purchase #3	$80.94	12.130%	$90.758	$90.76	$90.75	$90.80
Purchase #4	$5.60	9.854%	$6.1518	$6.15	$6.15	$6.20
Purchase #5	$113.64	9.473%	$124.4051	$124.41	$124.40	$124.40
Purchase #6	$226.28	6.772%	$241.6037	$241.60	$241.60	$241.60
Purchase #7	$85.60	5.544%	$90.3457	$90.35	$90.35	$90.30
7 purchase totals =	$606.17		$652.8164	$652.83	$652.80	$652.80