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	$61.70	11.589%	$68.8504	$68.85	$68.85	$68.90
Purchase #2	$52.62	6.528%	$56.055	$56.06	$56.05	$56.10
Purchase #3	$82.64	8.150%	$89.3752	$89.38	$89.40	$89.40
Purchase #4	$216.92	9.653%	$237.8593	$237.86	$237.85	$237.90
Purchase #5	$233.38	3.303%	$241.0885	$241.09	$241.10	$241.10
Purchase #6	$138.57	4.241%	$144.4468	$144.45	$144.45	$144.40
Purchase #7	$238.47	12.124%	$267.3821	$267.38	$267.40	$267.40
7 purchase totals =	$1,024.30		$1,105.0573	$1,105.07	$1,105.10	$1,105.20