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	$191.33	9.160%	$208.8558	$208.86	$208.85	$208.90
Purchase #2	$22.87	8.292%	$24.7664	$24.77	$24.75	$24.80
Purchase #3	$145.40	4.792%	$152.3676	$152.37	$152.35	$152.40
Purchase #4	$159.36	12.700%	$179.5987	$179.60	$179.60	$179.60
Purchase #5	$24.82	9.638%	$27.2122	$27.21	$27.20	$27.20
Purchase #6	$72.94	11.680%	$81.4594	$81.46	$81.45	$81.50
Purchase #7	$169.33	5.844%	$179.2256	$179.23	$179.25	$179.20
7 purchase totals =	$786.05		$853.4857	$853.50	$853.45	$853.60