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	$93.74	5.866%	$99.2388	$99.24	$99.25	$99.20
Purchase #2	$21.82	9.162%	$23.8191	$23.82	$23.80	$23.80
Purchase #3	$215.52	4.357%	$224.9102	$224.91	$224.90	$224.90
Purchase #4	$52.79	13.369%	$59.8475	$59.85	$59.85	$59.80
Purchase #5	$231.91	11.194%	$257.87	$257.87	$257.85	$257.90
Purchase #6	$109.55	11.300%	$121.9292	$121.93	$121.95	$121.90
Purchase #7	$241.48	9.683%	$264.8625	$264.86	$264.85	$264.90
7 purchase totals =	$966.81		$1,052.4773	$1,052.48	$1,052.45	$1,052.40