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	$238.50	12.207%	$267.6137	$267.61	$267.60	$267.60
Purchase #2	$160.86	10.693%	$178.0608	$178.06	$178.05	$178.10
Purchase #3	$217.69	10.841%	$241.2898	$241.29	$241.30	$241.30
Purchase #4	$163.90	12.757%	$184.8087	$184.81	$184.80	$184.80
Purchase #5	$66.59	7.864%	$71.8266	$71.83	$71.85	$71.80
Purchase #6	$61.72	8.153%	$66.752	$66.75	$66.75	$66.80
Purchase #7	$72.91	13.282%	$82.5939	$82.59	$82.60	$82.60
7 purchase totals =	$982.17		$1,092.9455	$1,092.94	$1,092.95	$1,093.00