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	$87.60	4.584%	$91.6156	$91.62	$91.60	$91.60
Purchase #2	$94.43	3.439%	$97.6774	$97.68	$97.70	$97.70
Purchase #3	$45.50	6.841%	$48.6127	$48.61	$48.60	$48.60
Purchase #4	$83.73	6.215%	$88.9338	$88.93	$88.95	$88.90
Purchase #5	$233.56	3.303%	$241.2745	$241.27	$241.25	$241.30
Purchase #6	$92.54	8.803%	$100.6863	$100.69	$100.70	$100.70
Purchase #7	$51.60	6.232%	$54.8157	$54.82	$54.80	$54.80
7 purchase totals =	$688.96		$723.6160	$723.62	$723.60	$723.60