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	$83.43	13.794%	$94.9383	$94.94	$94.95	$94.90
Purchase #2	$147.45	13.691%	$167.6374	$167.64	$167.65	$167.60
Purchase #3	$81.64	10.789%	$90.4481	$90.45	$90.45	$90.40
Purchase #4	$129.63	13.549%	$147.1936	$147.19	$147.20	$147.20
Purchase #5	$123.54	3.858%	$128.3062	$128.31	$128.30	$128.30
Purchase #6	$50.43	7.650%	$54.2879	$54.29	$54.30	$54.30
Purchase #7	$203.35	6.347%	$216.2566	$216.26	$216.25	$216.30
7 purchase totals =	$819.47		$899.0681	$899.08	$899.10	$899.00