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	$232.53	9.392%	$254.3692	$254.37	$254.35	$254.40
Purchase #2	$119.40	10.636%	$132.0994	$132.10	$132.10	$132.10
Purchase #3	$165.54	8.469%	$179.5596	$179.56	$179.55	$179.60
Purchase #4	$149.26	4.819%	$156.4528	$156.45	$156.45	$156.50
Purchase #5	$108.69	13.828%	$123.7197	$123.72	$123.70	$123.70
Purchase #6	$183.46	5.493%	$193.5375	$193.54	$193.55	$193.50
Purchase #7	$16.83	10.360%	$18.5736	$18.57	$18.55	$18.60
7 purchase totals =	$975.71		$1,058.3118	$1,058.31	$1,058.25	$1,058.40