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	$157.70	4.334%	$164.5347	$164.53	$164.55	$164.50
Purchase #2	$116.34	13.182%	$131.6759	$131.68	$131.70	$131.70
Purchase #3	$178.94	7.355%	$192.101	$192.10	$192.10	$192.10
Purchase #4	$130.86	5.505%	$138.0638	$138.06	$138.05	$138.10
Purchase #5	$156.98	8.864%	$170.8947	$170.89	$170.90	$170.90
Purchase #6	$143.68	5.796%	$152.0077	$152.01	$152.00	$152.00
Purchase #7	$59.37	12.493%	$66.7871	$66.79	$66.80	$66.80
7 purchase totals =	$943.87		$1,016.0649	$1,016.06	$1,016.10	$1,016.10