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	$22.58	8.509%	$24.5013	$24.50	$24.50	$24.50
Purchase #2	$9.96	13.601%	$11.3147	$11.31	$11.30	$11.30
Purchase #3	$47.71	13.384%	$54.0955	$54.10	$54.10	$54.10
Purchase #4	$86.76	4.146%	$90.3571	$90.36	$90.35	$90.40
Purchase #5	$61.84	3.860%	$64.227	$64.23	$64.25	$64.20
Purchase #6	$82.25	9.692%	$90.2217	$90.22	$90.20	$90.20
Purchase #7	$14.80	12.594%	$16.6639	$16.66	$16.65	$16.70
7 purchase totals =	$325.90		$351.3812	$351.38	$351.35	$351.40