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	$233.56	10.408%	$257.8689	$257.87	$257.85	$257.90
Purchase #2	$69.40	4.401%	$72.4543	$72.45	$72.45	$72.50
Purchase #3	$168.83	13.247%	$191.1949	$191.19	$191.20	$191.20
Purchase #4	$94.31	3.491%	$97.6024	$97.60	$97.60	$97.60
Purchase #5	$86.46	9.455%	$94.6348	$94.63	$94.65	$94.60
Purchase #6	$186.69	7.438%	$200.576	$200.58	$200.60	$200.60
Purchase #7	$247.87	9.391%	$271.1475	$271.15	$271.15	$271.10
7 purchase totals =	$1,087.12		$1,185.4788	$1,185.47	$1,185.50	$1,185.50