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	$249.90	12.638%	$281.4824	$281.48	$281.50	$281.50
Purchase #2	$248.37	5.231%	$261.3622	$261.36	$261.35	$261.40
Purchase #3	$201.77	12.429%	$226.848	$226.85	$226.85	$226.80
Purchase #4	$53.72	3.155%	$55.4149	$55.41	$55.40	$55.40
Purchase #5	$13.89	9.747%	$15.2439	$15.24	$15.25	$15.20
Purchase #6	$38.59	4.741%	$40.4196	$40.42	$40.40	$40.40
Purchase #7	$65.86	8.789%	$71.6484	$71.65	$71.65	$71.60
7 purchase totals =	$872.10		$952.4194	$952.41	$952.40	$952.30